Someone may have made this point somewhere else already, but there’s really no mystery in Americans getting fatter if we condition on the trajectory of mean calorie intake. Mean calorie intake has gone up by about 20% from 1970 to 2010 in the US, and mean body weight apparently went up by around 15% in the same period.
If we make a simplification and assume that you expend energy at a rate proportional to your body mass (reasonable because work has units of mass×distance2×time−2), we would roughly expect that increasing your calorie intake by 20% permanently would mean you either have to dissipate this energy in the form of excess sweating etc. or you have to store it somehow. If we make a further simplification and assume you don’t compensate for your excess calorie intake by excess heat dissipation (which seems roughly correct empirically), we end up with your body mass having to eventually go up by 20% so that your new energy expenditure matches your higher calorie intake.
In other words, a naive picture of the energy balance of the human body suggests we should expect long-term calorie intake and long-term body mass to be roughly proportional to each other. This is close to what we find empirically: 20% increase in mean calorie intake together with a 15% increase in mean body mass from 1970 to 2010. Any difference here can be explained away by short-run convergence dynamics, which tend to be much more complicated than the long-run energy balance relations.
Here’s a passage from Slime Mold Time Mold that supports this:
Partly this is because once you gain weight, you burn more calories (because it takes more energy to move and maintain physiological function) and you need to eat more calories to maintain your weight. Studies show that people with obesity eat and expend more calories than lean people. From this study, for example, consider this sentence: “TDEE was 2404±95 kcal per day in lean and 3244±48 kcal per day in Class III obese individuals.” From this perspective, the average daily consumption per Pew being 2,481 calories per day doesn’t seem like much — that’s about what lean people expend daily. Obese individuals generally burn 3000+ kcal/day, and while not every modern person is obese, it does make the increase from 2,025 calories per day in 1970 to about 2,481 calories per day in 2010 look relatively small.
Global warming is a good analogy here. In the long run we know e.g. the greenhouse effect should lead to a higher global mean temperature because of the energy balance of the Earth’s climate system. However, in the short run there are many places that can soak up energy: deep ocean dynamics, for instance, cause convergence to climatic equilibrium to take time on the order of hundreds or thousands of years. The human body is similar.
This might seem obvious to some people but Slime Mold Time Mold has said before that the increase from ~ 2000 kcal to ~ 2400 kcal in mean calorie intake is small. The exact quote from them is below:
It’s true that people eat more calories today than they did in the 1960s and 70s, but the difference is quite small. Sources have a surprisingly hard time agreeing on just how much more we eat than our grandparents did, but all of them agree that it’s not much. Pew says calorie intake in the US increased from 2,025 calories per day in 1970 to about 2,481 calories per day in 2010. The USDA Economic Research Service estimates that calorie intake in the US increased from 2,016 calories per day in 1970 to about 2,390 calories per day in 2014. Neither of these are jaw-dropping increases.
It’s indeed small compared to the overfeeding studies they consider (which can involve people going up to 10,000 kcal/day in calorie consumption) but those studies are short-term and as a consequence are mainly informative about convergence dynamics and not about equilibrium sensitivities.
They later tried to address this because people picked up on it and eventually said “well, even if the 20% increase explains the obesity epidemic, that still leaves the question of why people are eating more open”. I think this is bizarre: to me it’s quite obvious that in the long run more calorie intake has to lead to higher body mass, though not necessarily in a proportional way as I’ve idealized above. They should have been focusing on the causal channel going through calorie intake from the start. Instead, it seems like to them this was a secondary channel to fall back on.
Edit: I want to point out how disturbing it is that both the post itself and my comment have been receiving many downvotes from people who don’t think it’s worth their time to explain what they think is wrong with either of them. If you want to carry on doing that then more power to you, but it’s a mode of behavior that lowers my opinion of LW as a forum, especially when the agreement karma is available to express disagreement.
They later tried to address this because people picked up on it and eventually said “well, even if the 20% increase explains the obesity epidemic, that still leaves the question of why people are eating more open”. I think this is bizarre: to me it’s quite obvious that in the long run more calorie intake has to lead to higher body mass, though not necessarily in a proportional way as I’ve idealized above. They should have been focusing on the causal channel going through calorie intake from the start. Instead, it seems like to them this was a secondary channel to fall back on.
Calorie intake does lead to higher body mass, and 20% is a big increase. I do not disagree with you, there. However, something made people eat 20% more calories, be it palatable foods, lithium (though, now, probably not), PFAS, etc.
My hope (desperate hope, really) is if we can find the cause of the 20% increase, we can reverse the obesity trends.
I agree with you—something is indeed making people eat more and all the interesting questions are about what that is.
I wouldn’t have written my comment if Slime Mold Time Mold had not initially claimed that 20% is a small increase and contrasted it with various overfeeding studies to “demonstrate” how it could not be an important causal node in explaining the obesity epidemic. This argument was particularly bad because they neglected to draw the important distinction between equilibrium effects and transitory or convergence dynamics.
400 extra calories over a year (assuming 3500 calories = 1 pound) is an extra 41.7 pounds per year.
In reality, you’ll stop gaining weight at some point if you increase your caloric intake once and never change it again, because your energy expenditure will rise.
But even taking that into account, it does seem to me that 456 extra kcal per day is way too much.
Here’s an illustrative calculation. Herman Pontzer has the following equations relating body weight to total daily energy expenditure in his book (figure 3.4):
TDEE={766⋅ln(weight in kg)−1582,for women1105⋅ln(weight in kg)−2613,for men
The average woman in the US weighed 65.5 kg in the 1970s, and 78 kg in the 2010s, so this predicts a TDEE increase of only 134 kcal for women. For men, the figure is 160 kcal. Those numbers are about a third of 456 kcal. So yes, a 456 kcal in average daily energy intake would be a jaw-dropping increase.
Of course, this 456 kcal number is based on self-report data, so it’s not likely to be that accurate. Stephan Guyenet mentions a better estimate on The Hungry Brain based on food disappearance data from the USDA, which is only 218 kcal/day, much closer to my estimates of how much TDEE has changed.
I agree with Eliezer et al. that CICO by itself cannot explain the obesity epidemic, but “a 456 kcal increase is not that much” is a bizarre argument.
Since this seems like a question at the center of this whole thing, I just wanted to double check using other sources. Using [this](https://www.omnicalculator.com/health/tdee) calculator with the “little/no exercise” setting, I see
Female; 36; 5′4″
Weight: 65.5 kg → 78 kg
TDEE: 1596 → 1746
Diff: 150 kcal/d
If we set it to “moderate exercise”, the gap increases to 194 kcal/d
If something is making fat cells want to expand more and give up fat less easily, a corresponding lack of glucose or triglycerides in the bloodstream will, obviously, cause people to eat more. Early studies in overfeeding before the obesity epidemic showed that you had to overfeed people a LOT to make them gain a small amount of weight, which was immediately lost after overfeeding stopped. This is how human metabolisms used to work, before something broke them.
Imagine somebody with cancer, maybe before surgery existed and people would just walk around with giant tumors. The tumor increases your weight. The metabolic input to increase the tumor has to come from somewhere. If you measure the food intake of the person with the tumor, they’ll probably eat more, maybe possibly exercise less, over that period. It doesn’t mean they can cure their cancer by eating moderately less in proportion to how much dietary intake increases when you have a tumor; eating less would make them hungry and less active, but wouldn’t shrink the tumor, which can just go on growing regardless.
People are getting fat, so they have to eat more.
Trust me, we’ve tried eating only untasty food. It’s not that.
I think saying “we” here dramatically over-indexes on personal observation. I’d bet that most overweight Americans have not only eaten untasty food for an extended period (say, longer than a month); and those that have, found that it sucked and stopped doing it. Only eating untasty food really sucks! For comparison, everyone knows that smoking is awful for your health, it’s expensive, leaves bad odors, and so on. And I’d bet that most smokers would find “never smoke again” easier and more pleasant (in the long run) than “never eat tasty food again”. Yet, the vast majority of smokers continue smoking:
A personal observation regarding eating not tasty food:
I served in the Israeli army, eating 3 meals a day on base. The food was perfectly edible… But that’s the best I can say about it.
People noticeably ate less—eating exactly until they weren’t hungry and nothing more than that, and many lost a few kilos.
Adding my anecdote to everyone else’s: after learning about the palatability hypothesis, I resolved to eat only non-tasty food for a while, and lost 30 pounds over about four months (200 → 170). I’ve since relaxed my diet a little to include a little tasty food, and now (8 months after the start) have maintained that loss (even going down a little further).
Slightly boggling at the idea that nuts and eggs aren’t tasty? And I completely lose the plot at “condiments”. Isn’t the whole point of condiments that they are tasty? What sort of definition of “tasty” are you going with?
This sounds like a pretty intense restriction diet that also happens to be unpalatable. But the palatable foods hypothesis (as an explanation for the obesity epidemic) isn’t “our grandparents used to only eat beans and vegan sausages and now we eat a more palatable diet, hence obesity.” It’s something much more specific about the palatability of our modern 20th/21st century diet vs. the early 20th century diet, isn’t it? What’s the hypothesis we could test that would actually help us judge that claim without inadvertently removing most food groups and confounding everything?
I’m going to bury this a bit deeper in the comment chain because it’s no more indicative than Eliezer’s anecdote. But FWIW,
I am in the (very fortunate) minority who struggles to gain much weight, and has always been skinny. But when I have more tasty food around, especially if it’s prepared for me and just sitting there, I absolutely eat more, and manage to climb up from ~146 to ~148 or ~150 (pounds). It’s unimaginable that this effect isn’t true for me.
Yeah, that sounds right—with a non-broken metabolism, eating lots and lots of tasty food that’s just prepared and sitting there, to your heart’s content, should totally result in about 4 pounds of weight gain, all the way up to 150 pounds.
Do you have any empirical evidence for either of the following?
Farmers were historically wrong to think that free-feeding their animals would tend to fatten them up, OR they didn’t believe it has that effect.
Prior to the more recent novel contaminants, humans are an exception among animals in this general trend, that free-feeding tends to fatten animals up.
Actually I’d ask about the effect of free-feeding non-domesticated animals on ecologically realistic food, rather than free-feeding cows bred to gain weight using grains.
Why “ecologically realistic food”? And which types of realism are you going to pick?
Overfeeding and obesity are common problems in pets, which are mostly not bred to gain weight the way cows are.
My family has kept many kinds of animals. If you give bunny rabbits as much veggies as they want, a large fraction becomes obese. And guinea pigs too. And for their own favorite foods, tropical fish do too. Cats too.
In fact, I have never noticed a species that doesn’t end up with a substantial fraction with obesity, if you go out of your way to prepare the most-compelling food to them, and then give that in limitless amounts. Even lower-quality, not-as-compelling foods free-fed can cause some obesity. Do you even know of any animal species like this?!
If there is large variation in susceptibility (which there would be) to the ostensible environmental contaminant, there should be species that you can free-feed and they don’t get obesity.
I agree that most animals will become overweight if given unlimited tasty food. Two counter examples in my life were a cat and a hamster. Both only became overweight in old age—with unlimited food and many treats. Caveat—the hamster didn’t look fatter than normal hamsters, but maybe all hamsters are fat.
Just adding my own anecdote here, literally every time that I can recall overeating out of my own volition, it was because the food was tasty or otherwise satisfying. The connection between how tasty a food is, and how likely I am to overeat it, is such a strong connection that it might as well be treated as a law of nature.
Doesn’t sound obviously true for me? I obviously won’t overeat food if it’s disgusting, but I’d say I’m more likely to overeat rice cakes than chocolate, for example. A lot of milder foods feel easier for me to overload on.
That’s interesting. One caveat I should add is that I was referring to calorie overconsumption, as opposed to volume overconsumption. Rice is not very calorie dense, making it relatively easy to become full without eating many calories.
Yeah, I was thinking of calories too. I think I could eat way too many rice cakes, reliably, day in and day out. Whereas eating even one Hershey’s bar starts to approach the level where I’d feel sick from the amount of chocolate, and want less of it around me in the future.
How are we defining tasty foods? I’m sure if the entire world voted, chocolate would clearly be more in the “tasty food” category than rice cakes, but perhaps you really like how rice cakes taste?
I think people are reading into my comment plenty of things that I didn’t say. My only actual claim is that the 20% increase in calorie intake is sufficient to “explain” or “account for” the increase in body mass from 1970 to 2010. It’s not small and the claim by SMTM that it’s small is inaccurate.
Your comment is about why people would be taking in more calories and I don’t think I have any special insight into that issue. I just don’t think SMTM has any special insight to it either. Your argument is obviously logically possible but I wouldn’t bet a lot of money that it would turn out to be the right explanation.
I’ll try rephrasing, somewhat overstating the strength of the reasoning (taking it from probabilistic to logical) in case that causes a basic idea to be clearly communicated that was obscured by probabilism.
If an increase in calorie intake was itself sufficient to produce an increase in fat mass in otherwise metabolically high-functioning adults, we’d have seen a different result from pre-obesity-epidemic experiments in overfeeding. This rules out the direction of causality “mere overeating” → “obesity”.
Any hypertrophy of fat cells, in turn, will causally require more nutritional intake to feed the hypertrophy, just like a cancer growing, or any other body part growing, will require more nutritional intake. So once you observe a cancer or a huge fat cell mass or any other diseased body part growing, you already know the person already took in that much food, both to grow the cancerous body part and sustain it; you shouldn’t be surprised to look back at the cancer patient’s caloric consumption record and find an excess; so finding that excess consumption shouldn’t update you at all about the cause of the malevolently growing body part.
You’re taking causality that must at least run from “fat cell hypertrophy” → “excess consumption” and already fully explains away the presence of an observed correlation, and then adding on a causal postulate that runs the other way—a direction of causality that would be theoretically possible in a world with no overfeeding experiments one way or the other, though not supported even there, since there is no otherwise unexpected observation which it explains; but which in our world is ruled out by the results of overfeeding experiments, which tested the results of experimental-intervention-produced excess calorie consumptions in metabolically healthy individuals before the obesity epidemic.
To further oversimplify the oversimplification: the logic you’re deploying for obesity would also work to conclude that overeating causes cancer, and therefore Proves Too Much.
The only reason why “overeating caused this huge fat mass to grow inside my body” sounds more plausible than “overeating caused this huge tumor to grow inside my body” is that the former theory follows the Sin Theory of Obesity in which obesity is a punishment for the sin of gluttony, while the latter theory is incongruent with simple just-world hypotheses as of the 21st century in Western societies. Both are ruled out by experiments showing that (in metabolically healthy individuals before the obesity epidemic) a randomized experimental intervention to add overeating does not produce obesity any more than it produces tumors.
The only reason why “overeating caused this huge fat mass to grow inside my body” sounds more plausible than “overeating caused this huge tumor to grow inside my body” is that the former theory follows the Sin Theory of Obesity
I think the first sounds more plausible because the story “humans store caloric excess as fat in times of plenty and burn it off in times of scarcity” is the kind of thing that we should have as a hypothesis-under-consideration before we look at the link between calorie intake and body mass. Whereas “humans store caloric excess as cancer” (or as fetuses) isn’t. And if that story is true, then “eating lots of caloric excess causes lots of fat to be stored” isn’t automatically true, but again it’s definitely something we should have under consideration.
So if your line here is meant to be taken a priori—that is, if you’re saying “even without actually looking at the link between caloric intake and body mass, there’s no reason to believe overeating-causes-fat any more than you’d believe overeating-causes-cancer”, then it seems just wrong.
Maybe you meant it a posteriori? Something like “okay but overeating studies show that eating lots of caloric excess doesn’t by default cause lots of fat to be stored, so you no longer have a plausible explanation”?
But then at least two other reasons come to mind for why overeating-causes-fat might still seem more plausible than overeating-causes-cancer. One is that someone might not believe that studies show what you think they show. Another is that someone might just be bad at propagating updates. Currently, these both seem more likely to me than your “sin theory” theory.
I strongly disagree with this interpretation of those overfeeding studies. From what I can tell (though I couldn’t access every study SMTM cites), “overfeeding” is usually defined relative to the output of one of the typical BMR/TDEE estimation formulas given a person’s parameters, not based on actual measurement of a subject’s TDEE. Those formulas are fine for a baseline guess, but even the most accurate ones are going to be substantially off in either direction for a fair number of people! Some of the difference is unaccounted-for NEAT, some of it is differences in absorption efficiency, some of it is probably other factors we don’t understand yet. Given the known reality of interpersonal variation in what your actual calories in and out are relative to their naive estimates, some subjects not gaining weight while “overfeeding” is exactly what you’d expect to see.
A fun fact: my estimated “effective TDEE” is (averaged over months) pretty consistently around 3300 cal/day for the past 18 months—rarely more than +/- 100 cal/day off in either direction—whereas the best formula I could find (using my body fat %, as actually-measured by a DEXA scan) says it should be something more like 2600-2800 cal/day. This is based on weighing my body daily and recording the caloric intake from actually-everything I eat, almost always weighing food when necessary rather than coming up with estimates.
I think I understood what you’re saying the first time around and again I agree that your account of things is certainly possible, but even in your case the tumor or fat mass has to be sustained by calorie consumption from the outside. The increase in calorie intake we’ve seen is about the amount we would have expected if someone had just told us that people are 15% fatter on average without any increase in exertion or heat dissipation to compensate for that.
Another way to say this is that I’m just making a claim about the conditional expectation E[average body mass increase | average calorie consumption increase = 20%] and pointing out this expectation is not far off from the actual observed body mass increase we see. In that sense the increase in calorie intake can account for the increase in body mass in correlational terms. The question of why both of these variables went up, though, is difficult and their level is obviously not determined by this argument.
Externally, why people feel the need to keep eating until they become obese is not a question with a clear (to me) answer. It could be because there is some process that’s operating in the body that’s taking priority over other activities and hoarding a lot of the energy intake to produce fat cells, which I think is your story. However, it could also be that some part of the brain is malfunctioning and leading the lipostat to be poorly calibrated. It could also be that the food you’re eating messes with the natural feedback loops in your body that are supposed to make you feel full when you’ve eaten enough.
I think this question is interesting and your account is logically possible. I just think that
I don’t have any special insight into which account is right, and
I don’t think your particular explanation is favored that much over other competing explanations.
I don’t think the overfeeding experiments provide strong evidence for your scenario, though I agree that they should be a Bayesian update in favor of accounts in that broad neighborhood. What would convince me is experiments which involve smaller increases in calorie intake but sustained over much longer periods of time, on the order of a year or so. If such experiments failed to find an effect that would be a strong update for me towards your view. Right now I buy the cancer analogy on conceptual grounds but I don’t think we have enough evidence to conclude obesity is like cancer in this regard, though it very well could be the case.
To give an analogy of my own, the overfeeding studies look similar to attempts to settle disputes about which programming languages are best for productivity by asking undergraduates to complete some simple tasks in them over the course of a few weeks. What really matters is how you do when you’re working with big and complex software in the real world that has to be developed and maintained by large teams with turnover for years, sometimes decades; but that obviously doesn’t lend itself to a simple experimental design so people still keep arguing about it.
“Pregnancy” probably isn’t a thing. “Pregnant” people eat around 500 more calories per day. This is sufficient to explain all the weight gain from “pregnancy” without supposing anything other than thermodynamics at work—anyone who eats an extra 500 calories per day will probably gain that much weight over the course of 40 weeks.
I think Ege’s alleging that SMTM presented two causal graphs:
calories → ? → weight gain
calories → weight gain
Ege’s saying that 2 is simpler and sufficient, so we don’t need to posit a ? in the middle.
You’re pointing out that we still need to address a third causal graph:
? → calories → weight gain
Edit: And maybe that there’s also a scenario where ?, calorie intake, and weight gain are all in some complex interrelationship. Maybe contaminants cause more fat deposition and less energy and more hunger, thereby increasing weight gain per calorie, increased calorie intake, and increased contaminant intake via food. Or something.
Ege’s agreeing with you, but wants to emphasize that this is compatible with criticism of SMTM’s alleged emphasis on graph 1.
Note: I say “alleged” only because I’m sidestepping evaluating the truth of Ege’s claim. Just trying to clarify what it is (AFAICT).
I don’t agree with this presentation of what I’m saying.
I’m not terribly sure what SMTM means when they say “the increase in calorie intake is small”, but all possible interpretations of their claim seem wrong. For instance, one plausible interpretation in causal graph lingo is “if you applied the do operator on calorie intake and raised it by 20%, we would have seen an increase in body mass that’s significantly smaller than what we’ve actually seen”. I think this claim is wrong, basically for long-run energy balance reasons.
I’m not saying anything else about the structure of the causal graphs, which could be arbitrarily complicated and involve arbitrarily many nodes and dependencies. I’m just saying that if you apply the do operator on calorie intake and raise it by 20% then you’d get an increase in mean body mass that’s about as big as what we’ve seen.
Thanks for clarifying that I misrepresented your view. Based on your response here, you’re pointing out that there’s a strong correlation between increased caloric intake at the population level, and increased obesity. You are also saying that the explanations you’ve read from SMTM for why this correlation exists seem wrong, and also that they underestimate the magnitude or importance of the caloric intake.
WRT Eliezer’s arguments, you seem to be agreeing that there may be some underlying force(s) causing that increased caloric intake. However, you are very uncertain about which, if any, of the hypothesized forces(s) are the true causes of increased caloric intake.
Eliezer and others seem to be perhaps mistakenly interpreting you as denying the existence of, or “need for,” a deeper explanation for increased caloric intake and consequent weight gain. You are confused about why they are making this mistake.
I’m not sure who is “to blame” for the miscommunication but I suspect I simply was not clear enough in my top comment. Now it’s likely too late to clear up the issue for most readers as they won’t be following the developments in this thread.
I’m just saying that if you apply the do operator on calorie intake and raise it by 20% then you’d get an increase in mean body mass that’s about as big as what we’ve seen.
This is “assuming there’s no link “increased calorie intake → increased energy expenditure”″, right? I think one of the things Eliezer is saying is that there seems to have been such a link in the past and now there isn’t / it’s much weaker.
That’s not quite true—there is at least the naive link that a higher equilibrium body mass leads you to expend more energy in daily activities even if you exercise the same amount as before. In my very naive model I assume these are directly proportional, but Natalia cites some better research that does a log-linear regression of calorie expenditure on equilibrium (I think? I didn’t check this part) body mass which seems to be more accurate empirically.
I think it’s unclear whether we had the link you mention in the past, too. We definitely had a correlational link: people who did hard labor and ended up exercising a lot every day took in much more calories, as we would expect, and they were generally not obese. However, I think my argument would work just as well in the past if you just applied the do operator on calorie intake per day and looked at the causal impact on equilibrium body mass, as I don’t think there’s evidence that there’s a big downstream link from calorie intake per day to exercise.
I don’t understand why you’re “retrying”. I already agree with your point and you not saying “yes, you already agree with me” is quite confusing to me. As I say in my comment:
Externally, why people feel the need to keep eating until they become obese is not a question with a clear (to me) answer. It could be because there is some process that’s operating in the body that’s taking priority over other activities and hoarding a lot of the energy intake to produce fat cells, which I think is your story.
Do you think this characterization of your position is unfair or wrong? If so, why?
As far as I can see the only object-level point I disagree with you about is that I don’t think the evidence for obesity being like cancer or pregnancy is as strong as you seem to think it is. It’s definitely possible for it to be like that but I would bet against it at even odds. I explain this here:
I don’t think the overfeeding experiments provide strong evidence for your scenario, though I agree that they should be a Bayesian update in favor of accounts in that broad neighborhood. What would convince me is experiments which involve smaller increases in calorie intake but sustained over much longer periods of time, on the order of a year or so. If such experiments failed to find an effect that would be a strong update for me towards your view. Right now I buy the cancer analogy on conceptual grounds but I don’t think we have enough evidence to conclude obesity is like cancer in this regard, though it very well could be the case.
On top of that I also have a separate disagreement with you about emphasis in the context of my comment, since the point of my top comment is to draw attention to 400 kcal/day not being a small increase in calorie intake. You agree with me about this but you just don’t think it’s worth focusing on, probably because you think it’s a trivial observation. I still think it’s something that should be corrected given that SMTM explicitly said that it’s a small increase.
As far as I can see the only object-level point I disagree with you about is that I don’t think the evidence for obesity being like cancer or pregnancy is as strong as you seem to think it is.
Some people certainly are obese because of literal cancer and literal pregnancy. We seem to have strong evidence for that.
The interesting question is about how much of the obesity pandemic is explainable by such factors and not whether evidence for such factors exists.
We certainly don’t see enough pregnancy and cancer to explain the obesity epidemic but there might be other factors that are similar but harder to see. Thermodynamic arguments don’t help us rule out other effects that are similar to pregnancy/cancer.
I agree with everything you said, so again I’m confused why you thought you should make this comment.
I feel like I don’t really disagree with most of the commenters but they either think I do disagree with them or that I did a very bad job of communicating exactly what my point was. It’s hard for me to understand.
I still stand by this claim, again with the caveat that you take it as a correlational use of the word “explain” (which is not at all uncommon e.g. when talking about “fraction of explained variance” and so forth) and not one that suggests a causal explanation of the form “people wanted to eat more food, so they ate more food, so they got fatter as a result”.
Ok. My main point is just to clarify that other people are reading you as talking about explanation in general, not just strictly correlational explanation (if that’s what’s happening).
I do also think that’s not a great use of the word “explain” and “mystery”, because it’s not why the colloquial word is useful. The colloquial words “explain”/”mystery” are useful because they index “more information and ideas given/needed about this”. So just because X correlationally explains Y, and X is true, doesn’t mean there’s no mystery about Y.
I never said there’s no mystery about Y, just that there’s no mystery about Y being true conditional on X being true.
It’s a fair point that my usage of “explain” and “mystery” confused some people but I’m not too sure how else I would have made my point. Should I have said “people today are eating about as much more compared to the past as we would expect given how much fatter they’ve gotten”?
Someone may have made this point somewhere else already, but there’s really no mystery in Americans getting fatter if we condition on the trajectory of mean calorie intake.
Read literally, this says: There’s a mystery of why intake went up. Conditioned on intake up, there’s no mystery of why fat went up. I think this isn’t right. If we agreed that sustained high intake implies weight increase, it’s still not right. That’s because conditional probability isn’t the same as explanation, and if there’s a mystery, what we’re after is explanation. That’s one of the points of the tumor example: If fat causes intake, then saying “there’s no mystery about fat” is pointing away from the explanation of intake, which is that fat causes intake and something causes fat.
They later tried to address this because people picked up on it and eventually said “well, even if the 20% increase explains the obesity epidemic, that still leaves the question of why people are eating more open”. I think this is bizarre: to me it’s quite obvious that in the long run more calorie intake has to lead to higher body mass, though not necessarily in a proportional way as I’ve idealized above. They should have been focusing on the causal channel going through calorie intake from the start. Instead, it seems like to them this was a secondary channel to fall back on.
Taken literally, this seems to be consistent with beliefs of people who disagree with you? It’s just that they have different conclusions about the causality going through calorie intake. Interpreted that way, I don’t see how this statement is consistent with saying “there’s really no mystery in Americans getting fatter”.
I don’t understand your objection. I never made any claims about causality. My whole argument is about energy balance, which says nothing about causality.
On the other hand, I think it’s just true that conditioned on the increase in calorie intake there’s no mystery in the increase in body mass. I don’t understand why you’re disputing this point. You can say this is not an interesting observation (which I agree with, though as far as I can tell SMTM did not, which is why I wrote my comment) but I don’t see how you can say it’s not right.
My impression is that some people are engaging in a bizarre combination of steelmanning SMTM’s point while strawmanning my own. SMTM didn’t make the best version of the claim they could have made, they made the actual claim that I quote in my post. I think their claim is wrong. Do you disagree with this or not?
Meta: my interest here is to see if there are miscommunications here that I can clear up. I’m not carefully following the object-level debate. (In particular, I think that you Ege should feel extremely free to ignore what I’m saying as unhelpful to you; if I’m not helping you understand what’s happening in the thread then I’m not doing what I’m trying to do.)
I don’t understand your objection. I never made any claims about causality. My whole argument is about energy balance, which says nothing about causality.
On the other hand, I think it’s just true that conditioned on the increase in calorie intake there’s no mystery in the increase in body mass. I don’t understand why you’re disputing this point.
(Note: you did mention causality in the passage I quoted: “They should have been focusing on the causal channel going through calorie intake from the start.” That’s not a claim about what causes what, but it is a claim about what questions are the right questions to ask.)
I’m pointing at the word “mystery”. I’m saying that to me, “mystery” means “explanation wanted”. I’m saying that just because P(X|Y) is high, doesn’t mean Y is a good explanation of X. (For a silly example, setting Y=”X and 2+1=3″ makes P(X|Y) = 1 and is obviously doesn’t explain anything.) I agree (based on my preconceptions, ~0 independent data) that P(body mass high | high sustained intake in the wild) is high. My read of some of the comments on your comment, e.g. Yudkowsky’s, is that they are taking you to be saying “high intake explains fat, such that there is no further interesting question about fat, though there may be further questions about why high intake”, based on the passages from your comment I quoted. Reading your comment closely, you didn’t actually say that, if by “conditional on Y, there’s no mystery about X” you mean “P(X|Y) is high”. In fact, what you said is consistent with believing that “Alice is fat” explains (in the contextually relevant sense) that “Alice has high intake”, and you recommend that if you believe this then you should “focus[] on the causal channel going through calorie intake”, i.e. investigate why Alice is fat in order to explain her high intake.
SMTM didn’t make the best version of the claim they could have made, they made the actual claim that I quote in my post. I think their claim is wrong. Do you disagree with this or not?
I don’t know. I think your argument makes sense, but the actual situation is going to be more complicated.
Do you know, if we also observe an obesity-epidemic in the subgroup of people who average 25k+ in daily steps? That step-requirement is a good, high standard of “metabolically healthy” to isolate. I belong in that group these days and it feels natural, relaxed and I feel far more energetic than when I was averaging 7k daily steps and was the sedentary nerd cliché, about a year ago. Now I am a nerd, who takes two walks per day, almost never sits and either stands or uses his office treadmill when on the computer. Even before, I never really got fat. But I feel, that I might not have been “metabolically healthy”, because now I feel better. So I strongly suspect that a far higher than average step-count is a hard requirement for being “metabolically healthy”.
I hear that “pregnant” people also do less mountain-climbing, even if they were exercising healthily before. No wonder they gain weight! Do we even need to postulate “pregnancy” as a condition, when their caloric intake and reduced exercise seems adequate to explain all of the observed weight gain?
I was not responding to your pregnancy-argument, but to your post higher up in this subthread from 3 days ago. The threading makes this a bit confusing. Also should have specified what I was responding to the last paragraph: ”Both are ruled out by experiments showing that (in metabolically healthy individuals before the obesity epidemic) a randomized experimental intervention to add overeating does not produce obesity any more than it produces tumors.”
Is there actually an obesity epidemic among people who walk more than 25k steps per day? (or is something like that currently known).
EDIT: I suppose my hypothesis is: Living a non-sedentary lifestyle meaning less than 20 minutes of sitting per day, 25k-ish steps per day somewhat equally spread out over all waking hours makes the “weight-gain -=> obesity”-phenomenon impossible, because it’s a sufficient requirement for robust metabological health. If that was true, it might not answer what is behind the obesity epidemic. But that’s what I would study, to check if it’s a cure or reliable prevention.
I’d say 90% chance of this being true, but mostly on intuition and with high model uncertainty. And I don’t know, if we know enough to answer this question, because non-sedentary lifestyles like that are fairly niche in all Western societies. But I recently figured out, that they’re not all that hard to adopt.
EDID2: Actually, I’d say the 90% applies to it being “reliable prevention”. No clue, how curative that would be. I never had to really lose more than a couple kg of fat. [and “had to” is really exaggerating a lot] From what I observe, it seems somehow impossible for really fat people to become not fat, despite heroic struggles which have always been strange to observe from the outside.
Is there any solid evidence that walking 25k steps per day will solve the obesity epidemic? I ask this because it’s genuinely a remarkable claim, one that if verified and implemented would save huge numbers of lives and hundreds of billions in medical expenses. The literature mostly seems to indicate that increased exercise doesn’t have dramatic effects on obesity.
There is not. That’s why I was asking him if he knows. I was not interested in the effect of exercise. Exercise means, you do some activity a couple times per week. I’m interested whether the obesety epidemic only affects the sedentary populatrion. And if being or becoming non-sedentary is protective or curative. 25k steps for me means, that my treadmill is running constantly when I’m on my computer. This is not really exercise. Movement is just my default state.
In that way, I have become closer to what an EAA-hunter-gatherer, than to a sedentary office worker does with his body. [or I would, if this had been my lifetime norm instead of something I still get used to] If the human body was sold as a machine, the sedentary lifestyle probably would void your warranty, because it’s rather extreme (dis)usage. Sedentary people being unhealthy is not surprising. It’s surprising that some sedentary people aren’t.
Anyway, “being in near-constant motion” is too specific/complicated a metric. So I’d just look for a step count high enough, that’s only feasibly doable by a non-sedentary person like me. Though, I guess any daily jogger can probably match or exceed 25k steps per day. The group of people whose 80th quantile waking hour still has >1k steps. That’s probably the better proxy, come to think of it.
All right, here’s my crack at steelmanning the Sin of Gluttony theory of the obesity epidemic. Epistemic status: armchair speculation.
We want to explain how it could be that in the present, abundant hyperpalatable food is making us obese, but in the past that was not so to nearly the same extent, even though conditions of abundant hyperpalatable food were not unheard of, especially among the upper classes. Perhaps the difference is that, today, abundant hyperpalatable food is available to a greater extent than ever before to people in poor health.
In the past, food cultivation and preparation were much more labor intensive than in the present, so you either had to pay a much higher price for your hyperpalatable food, or put in the labor yourself. Furthermore, there were fewer opportunities to make the necessary income from sedentary work, and there wasn’t much of a welfare state. Thus, if you were in poor health, you were much more likely in the past than today to be selected out of the class of people who had access to abundant hyperpalatable food. Obesity is known to be a downstream effect of various other health problems, but only if you are capable of consuming enough calories, and have access to food that you want to overeat.
Furthermore, it is plausible that some people, due to genetics or whatever, have a tendency to be in good health when they lack access to abundant hyperpalatable food, and to become obese and thus unhealthy when they have access to abundant hyperpalatable food. Thus there is a feedback loop where being healthier makes you more productive, which makes hyperpalatable food more available to you, which makes you less healthy, which makes you less productive, which makes hyperpalatable food less available to you. Plausibly, in the past, this process tended towards an equilibrium at a much lower level of obesity than it does today, because of today’s greater availability of hyperpalatable food to people in poor health.
It is also plausible that our technological civilization has simply made considerable progress in the development of ever more potent gustatory superstimuli over the past century. This is a complex optimization problem, and it’s not clear why we should have come close to a ceiling on it long before the present, or why just contemplating the subjective palatability of past versus present-day food would give us conscious awareness of why we are more prone to overeating the latter.
Both of these proposed causes are consistent with pre-obesity-epidemic overfeeding studies of metabolically healthy individuals failing to cause large, long-term weight gain: They suggest that the obesity epidemic is concentrated among metabolically unhealthy people who in the past simply couldn’t afford to get fat, and that present-day food is importantly different.
Adderall caused weight gain for me, and anecdotally also for a close friend of mine. Wellbutrin works, though, at least for me personally.
Lots of drugs have effects that vary wildly between different individuals (and they may even sometimes cause paradoxical effects), so I’m not sure that variance in response to amphetamines is necessarily that much of a hint about what is causing the obesity epidemic. If semaglutide works universally, or nearly so—and early studies are very promising—then that might be a strong hint as to what is causing the obesity epidemic.
If semaglutide works universally, or nearly so—and early studies are very promising—then that might be a strong hint as to what is causing the obesity epidemic.
Relatedly, this seems to be the distribution of weight changes on 15 mg of tirzepatide + lifestyle interventions, compared to lifestyle interventions alone (over 72 weeks, I think):
This guy says it’s fructose, plus salt and MSG. “Nature puts a “survival switch” in our bodies to protect us from starvation. Stuck in the “on” position, it’s the hidden source of weight gain, heart disease, and many other common health struggles. But you can turn it off.” I think he’s on to something; since I’ve been following his recommendations, I’ve been able to lose weight again ( ~9 kg since the end of April).
there’s really no mystery in Americans getting fatter if we condition on the trajectory of mean calorie intake. Mean calorie intake has gone up by about 20% from 1970 to 2010 in the US, and mean body weight apparently went up by around 15% in the same period.
I feel like you’ve missed SMTM’s central point. Sure, people are eating more. The main question is why people eat more. For example, I used to weigh 172 pounds in the Philippines 4 years ago; now I weigh about 192 in Canada. I used to think my overweight best friend was overfeeding me (well, he did), but since he moved away two years ago, I’ve actually gained weight somehow. I have a mild sense of being hungrier here. Presumably I am eating more, but why?
(Having said that, it looks like OP has done great work and this is a big red flag:)
I have attempted to make a comment on SMTM’s post linking to many of those studies, but they have not approved the comment. I have also attempted to contact them on Twitter (twice) and through email, but have not received a reply. All of this was over one week ago, and they have, since then, replied to other people on Twitter and approved other comments on their post, but haven’t commented on this. So I have no idea why their literature review excludes these studies.
...Note: I have attempted to make some of those points in the comment section of SMTM’s last post about lithium, but they never approved my comment....
...I have attempted to point this out by making a comment on their post, but they have not approved the comment....
(Having said that, it looks like OP has done great work and this is a big red flag:)
I have attempted to make a comment on SMTM’s post linking to many of those studies, but they have not approved the comment. I have also attempted to contact them on Twitter (twice) and through email, but have not received a reply. All of this was over one week ago, and they have, since then, replied to other people on Twitter and approved other comments on their post, but haven’t commented on this. So I have no idea why their literature review excludes these studies.
This isn’t the core of why I think you think that’s a red flag, but for the record I don’t think a week is that much time to respond to public criticism. I have many important emails I don’t reply to for longer.
I was thinking about comment approval more than response [and to make that clearer, I appended to my quotation above]. I’ve been perma-declined myself, not fun. Unfortunately if it’s approved now there will be a question as to whether it was approved now in response to an ultra-popular LW post.
I didn’t downvote you, I think you are eloquently arguing your point here! But I’m not entirely sure that the SMTM take is quite as bad as you make it out to be.
An average of 400 extra calories a day isn’t small on its own, but I think the SMTM argument is that it’s small compared to historical variation in caloric intake, and small compared to variation among humans in general today. In other words: there were likely times and cultures historically where average calories consumed was higher or lower than today by more than 400 calories—why wasn’t there an obesity epidemic previously when caloric intake was higher? Why, 100 years ago, were not the people eating 400 extra calories a day all obese?
I clearly found it more a more compelling argument that you do. Like you, I read the SMTM contaminant argument as essentially saying “historically there has been some process that kept calories consumed and calories expended in relative sync; that process has been disrupted”—and the argument that “400 calories per day explains the weight gain” isn’t really a counterargument to this?
I’ll point out one more aspect that I think you may want to consider. You write: “to me it’s quite obvious that in the long run more calorie intake has to lead to higher body mass”—but this is a statement that is somewhat circularly derived from today’s observations. 100 years ago, when very few people were obese, this statement might not be obvious at all. One might instead conclude that people with higher calorie intakes are compelled to burn more calories through manual labor, exercise, heat generation + sweating, etc.
Lastly, and obviously you know this on some level, but the fact that increased food consumption correlates with obesity, does not imply that that consumption causes obesity. SMTM argue that some external factor causes obesity; if so, increased food consumption would be a result of the body trying to maintain that weight. As you note, a 15% increase in body mass requires a 20% increase in caloric intake to sustain—if an external factor is increasing the lipostat, we would observe exactly what we observe today as well. It’s dangerous to point the causal arrow in either direction without more evidence.
And, speaking of evidence: the overfeeding studies are interesting in part because they at least resolve the question of whether and how much short-term overeating causes body mass increases; you’re 100% correct that they don’t resolve the question of whether long-term overeating also causes body mass increases, and it would be super interesting to see if a long-term (say, 1 year) 400-calorie increase in consumption (that somehow doesn’t come from changes in diet; maybe just eat an extra 20% at every meal?) causes weight gain.
As far as I know, no one’s run a long-term weight gain study—but we do have the super confusing result that a 30-40% decrease in calories is hard to sustain and the resulting weight loss plateaus at about a 10% decrease [0], suggesting that there’s more going on than the simple linear relation.
An average of 400 extra calories a day isn’t small on its own, but I think the SMTM argument is that it’s small compared to historical variation in caloric intake, and small compared to variation among humans in general today. In other words: there were likely times and cultures historically where average calories consumed was higher or lower than today by more than 400 calories—why wasn’t there an obesity epidemic previously when caloric intake was higher? Why, 100 years ago, were not the people eating 400 extra calories a day all obese?
Variation among humans can be caused by variation in their metabolism (or variation in how much they exercise) that changes the amount of energy they expend per unit mass without being inconsistent with the energy balance argument. There’s a lot of place variation in the cross section can come from other than calories consumed—I don’t think that’s actually that relevant to understanding trends in obesity. Energy balance can hold at any level of calorie intake so the question is why you settle on one point of equilibrium and not all the others, given that you’re the one making the decisions about how much to eat.
As for historical data, I’m not convinced there’s ever been a time when mean calorie intake in a reasonably large country was ever as high as it is in the US today. There’s of course been plenty of variation but I’d expect the variation to show up in body mass if it were sustained.
I clearly found it more a more compelling argument that you do. Like you, I read the SMTM contaminant argument as essentially saying “historically there has been some process that kept calories consumed and calories expended in relative sync; that process has been disrupted”—and the argument that “400 calories per day explains the weight gain” isn’t really a counterargument to this?
I’m not really convinced by the claim that what’s happening now is historically unprecedented and I think most of the work there is being done by summarizing the phenomenon in terms of obesity statistics instead of mean body mass. I think if we looked at the historical trajectory of mean body mass it would not really look like anything exceptional is happening today in terms of some fundamental balance process being thrown off.
I want to repeat: the point of my comment is not that “why are people eating more now?” is a question that shouldn’t be answered; it’s that the claim about 400 kcal being too small of an increase is just wrong. If you agree with that then you should just agree with my comment because that’s the only claim I make.
As far as I know, no one’s run a long-term weight gain study—but we do have the super confusing result that a 30-40% decrease in calories is hard to sustain and the resulting weight loss plateaus at about a 10% decrease [0], suggesting that there’s more going on than the simple linear relation.
I think my argument says nothing about how hard to sustain a decrease in calorie intake is—it’s consistent with your body making arbitrarily strong protests at having to burn its stores of fat and try to induce you to eat more to compensate. I’m agnostic on that point and I think it’s obviously an interesting question to look into.
Farm laborers historically ate a lot of calories just to be able to get through their days. Their calories weren’t very appetizing, but they had to eat a lot because they burned a lot.
That makes sense to me but I’d really need to see the data on how many calories they ate in 1700. I notice I would still be surprised if an average farm laborer in 1700 in prime age ate more than 2400 kcal/day. It’s not really relevant to my main point but if you have some data proving that I would be interested to see it.
Per Jeffrey L. Singman, Daily Life in Medieval Europe, Westport, Connecticut: Greenwood Press, 1999, P. 54 − 55 (and text copied from https://stores.renstore.com/food-and-drink/dietary-requirements-of-a-medieval-peasant), “A prosperous English peasant in the 14th century would probably consume 2 − 3 pounds of [rye, oats, or barley] bread, 8 ounces of meat or fish or other protein and 2 − 3 pints of ale per day”, which works out to about 3500 to 5000 calories per day.
That same page lists various farm chores as burning 1500-7500 calories over an 8 hour period, so assuming some mix of those plus the normal base calorie burning easily adds up to over 3500 calories.
This post (https://oureverydaylife.com/321257-the-peasant-diet.html) cites “research published at Eastern Kentucky University” to say that “an average medieval person burned between 4,000 and 5,000 calories per day … A typical diet for peasants delivered between 3,500 and 4,500 calories, about or just under the need.”
If you’d like I can do more academic research, but these independent sources all roughly corroborate each other so I’m personally satisfied.
One note is that the food eaten historically was much less appealing to eat. I don’t think they were eating 3 pounds of bread because they really liked oat bread, but rather that they needed it to survive doing hard manual labor for 8 hours a day.
Reported numbers vary quite a bit (perhaps in part because the physical activity intensity of training or warfighting also varies), but you might be interested to know that soldiers in training or active duty might hit something like 4000-5000 kcal/day in energy expenditure, maybe thousands more for outlier people and/or circumstances.
How much did city dwellers in the early 20th century eat? There must have been a period when people were not doing so much manual labor but before the obesity epidemic.
A lot of city dwellers then were doing manual labor (factory lines, construction), but I’m really not sure about the office workers from them. It’s a good question!
I think you are missing my point—which EY also makes above—that you are concluding that the calorie consumption increase causes obesity when in fact none of the evidence you provide supports pointing the causal arrow in that direction specifically.
We know obese people eat more, and we know that the greater fat mass has greater nutritional requirements.
The interesting question is not whether 400 calories are associated with the weight gain, clearly people are more obese now and also they eat 400 more calories on average, no one is disputing this. The interesting question is whether those 400 calories cause the weight gain or are caused by the weight gain. You are implying the former but there is not a lot of evidence in support of it—and other posters in this thread are chiming in with other evidence suggesting that 400 calories daily is well within normal historical variation, which is SMTM’s point that “400 extra calories causes weight gain” would be weird.
I think you are missing my point—which EY also makes above—that you are concluding that the calorie consumption increase causes obesity when in fact none of the evidence you provide supports pointing the causal arrow in that direction specifically.
No I’m not. I don’t understand why people are jumping to this conclusion—I said several times that “the only claim I’m making is X” but people keep attributing to me claims that are not X.
The interesting question is not whether 400 calories are associated with the weight gain, clearly people are more obese now and also they eat 400 more calories on average, no one is disputing this. The interesting question is whether those 400 calories cause the weight gain or are caused by the weight gain.
As I’ll repeat here again, the whole point of my comment is to question SMTM’s claim that a 20% increase in calorie intake is small. It’s not small. I agree otherwise that the interesting question is what caused people to shift from one equilibrium to another and talking about energy balance doesn’t help clear up that point. It’s just not the point I’m trying to make, though.
I think we are getting caught up in the definition of “small”. My original point earlier is that 400 calories is small compared with historical variation and variation among humans. Your original point is that 400 calories is more than enough to explain the weight gain and thus isn’t “small”. Those are different definitions of small, and are both true: 400 calories is small compared with historical and present variation among humans AND 400 calories is enough to explain the extra weight.
But the latter is obvious; clearly those 400 calories explain the weight gain, because people aren’t suddenly metabolizing air or water or other calorie-free inputs into extra weight, those fat cells are creating fat from calories people consume. I suspect people are ascribing other claims to you because “400 calories is not small—it’s enough to explain the excess weight” is only a useful claim in this context (“this context” being “what causes obesity?”) if you are also making the causative claim.
You insist you are not making the causative claim—so what exactly are you arguing re: the question of “what’s causing the weight gain?”
I mean, obviously the causal chain of weight gain is often going to go through caloric intake, but that doesn’t make caloric intake the root cause. For example, birth control pills, stress, and soda machines in schools all cause weight gain via increased caloric intake, but are distinct root causes.
As I said in my original comment, this might seem obvious to you but unfortunately it’s not obvious to everyone. In addition, it’s also not necessarily correct: you can get fatter because you expend less energy too. I think empirically it seems like just looking at calorie intake and assuming the energy expenditures are fairly flat is a decent story but that’s definitely not a conclusion you can reach a priori.
I wonder if the macronutrient rates shifted. This would influence the total calories you end up with because absorption rates are different for different macronutrients. How the food is processed also influences absorption (as well as the total amount of calories that may not be reflected on the package).
If these factors changed, calories today don’t mean exactly the same thing as calories in 1970.
Since FDA allows a substantial margin of error for calories, maybe producers also developed a bias that allows them to stay within this margin of error but show fewer calories on the package?
Maybe this is all controlled for in studies, dunno, I just did a couple of google searches and had these questions.
Edit: I want to point out how disturbing it is that both the post itself and my comment have been receiving many downvotes from people who don’t think it’s worth their time to explain what they think is wrong with either of them.
With +305 karma at the time of this writing the post has a very high karma count. If you look through recent post the only posts with higher karma are AI risk posts written by very senior people (Eliezer and Paul Christiano).
Without an easy way to look it up it wouldn’t surprise me if +305 karma puts the post in the top 20 posts by karma that exists on LessWrong2.0.
Ege Erdil was referring to a flurry of downvotes that this post got within ~30 minutes of being posted. I don’t remember the exact number, but at the time he made that edit the karma count was quite low due to them.
When I made the edit this was not the case and the post was getting quite a lot of downvotes. Apologies for not including a timestamp. It was like 30 minutes to 1 hour after the post had been published and at some point I think the post had more people that had voted on it than it had net karma with a couple of strong upvotes that I knew had been thrown into the mix, including my own.
I’ve downvoted this comment; in light of your edit, I’ll explain why. Basically, I think it’s technically true but unhelpful.
There is indeed “no mystery in Americans getting fatter if we condition on the trajectory of mean calorie intake”, but that’s a very silly thing to condition on. I think your comment reads as if you think it’s a reasonable thing to condition on.
I see in your comments downthread that you don’t actually intend to take the ‘increased calorie intake is the root cause’ position. All I can say is that in my subjective judgement, this comment really sounds like you are taking that position and is therefore a bad comment.
(And I actually gave it an agreement upvote because I think it’s all technically true)
I think the people who believe my comment is unhelpful aren’t understanding that the content in it that seems obvious to them is not obvious to everyone.
+1.
Someone may have made this point somewhere else already, but there’s really no mystery in Americans getting fatter if we condition on the trajectory of mean calorie intake. Mean calorie intake has gone up by about 20% from 1970 to 2010 in the US, and mean body weight apparently went up by around 15% in the same period.
If we make a simplification and assume that you expend energy at a rate proportional to your body mass (reasonable because work has units of mass×distance2×time−2), we would roughly expect that increasing your calorie intake by 20% permanently would mean you either have to dissipate this energy in the form of excess sweating etc. or you have to store it somehow. If we make a further simplification and assume you don’t compensate for your excess calorie intake by excess heat dissipation (which seems roughly correct empirically), we end up with your body mass having to eventually go up by 20% so that your new energy expenditure matches your higher calorie intake.
In other words, a naive picture of the energy balance of the human body suggests we should expect long-term calorie intake and long-term body mass to be roughly proportional to each other. This is close to what we find empirically: 20% increase in mean calorie intake together with a 15% increase in mean body mass from 1970 to 2010. Any difference here can be explained away by short-run convergence dynamics, which tend to be much more complicated than the long-run energy balance relations.
Here’s a passage from Slime Mold Time Mold that supports this:
Global warming is a good analogy here. In the long run we know e.g. the greenhouse effect should lead to a higher global mean temperature because of the energy balance of the Earth’s climate system. However, in the short run there are many places that can soak up energy: deep ocean dynamics, for instance, cause convergence to climatic equilibrium to take time on the order of hundreds or thousands of years. The human body is similar.
This might seem obvious to some people but Slime Mold Time Mold has said before that the increase from ~ 2000 kcal to ~ 2400 kcal in mean calorie intake is small. The exact quote from them is below:
It’s indeed small compared to the overfeeding studies they consider (which can involve people going up to 10,000 kcal/day in calorie consumption) but those studies are short-term and as a consequence are mainly informative about convergence dynamics and not about equilibrium sensitivities.
They later tried to address this because people picked up on it and eventually said “well, even if the 20% increase explains the obesity epidemic, that still leaves the question of why people are eating more open”. I think this is bizarre: to me it’s quite obvious that in the long run more calorie intake has to lead to higher body mass, though not necessarily in a proportional way as I’ve idealized above. They should have been focusing on the causal channel going through calorie intake from the start. Instead, it seems like to them this was a secondary channel to fall back on.
Edit: I want to point out how disturbing it is that both the post itself and my comment have been receiving many downvotes from people who don’t think it’s worth their time to explain what they think is wrong with either of them. If you want to carry on doing that then more power to you, but it’s a mode of behavior that lowers my opinion of LW as a forum, especially when the agreement karma is available to express disagreement.
Calorie intake does lead to higher body mass, and 20% is a big increase. I do not disagree with you, there. However, something made people eat 20% more calories, be it palatable foods, lithium (though, now, probably not), PFAS, etc.
My hope (desperate hope, really) is if we can find the cause of the 20% increase, we can reverse the obesity trends.
I agree with you—something is indeed making people eat more and all the interesting questions are about what that is.
I wouldn’t have written my comment if Slime Mold Time Mold had not initially claimed that 20% is a small increase and contrasted it with various overfeeding studies to “demonstrate” how it could not be an important causal node in explaining the obesity epidemic. This argument was particularly bad because they neglected to draw the important distinction between equilibrium effects and transitory or convergence dynamics.
Yeah, I definitely agree − 20% is a big increase. 400 extra calories over a year (assuming 3500 calories = 1 pound) is an extra 41.7 pounds per year.
I was so excited by A Chemical Hunger when it was coming out. Oh, well.
In reality, you’ll stop gaining weight at some point if you increase your caloric intake once and never change it again, because your energy expenditure will rise.
But even taking that into account, it does seem to me that 456 extra kcal per day is way too much.
Here’s an illustrative calculation. Herman Pontzer has the following equations relating body weight to total daily energy expenditure in his book (figure 3.4):
TDEE={766⋅ln(weight in kg)−1582,for women1105⋅ln(weight in kg)−2613,for men
The average woman in the US weighed 65.5 kg in the 1970s, and 78 kg in the 2010s, so this predicts a TDEE increase of only 134 kcal for women. For men, the figure is 160 kcal. Those numbers are about a third of 456 kcal. So yes, a 456 kcal in average daily energy intake would be a jaw-dropping increase.
Of course, this 456 kcal number is based on self-report data, so it’s not likely to be that accurate. Stephan Guyenet mentions a better estimate on The Hungry Brain based on food disappearance data from the USDA, which is only 218 kcal/day, much closer to my estimates of how much TDEE has changed.
I agree with Eliezer et al. that CICO by itself cannot explain the obesity epidemic, but “a 456 kcal increase is not that much” is a bizarre argument.
Since this seems like a question at the center of this whole thing, I just wanted to double check using other sources. Using [this](https://www.omnicalculator.com/health/tdee) calculator with the “little/no exercise” setting, I see
Female; 36; 5′4″
Weight: 65.5 kg → 78 kg
TDEE: 1596 → 1746
Diff: 150 kcal/d
If we set it to “moderate exercise”, the gap increases to 194 kcal/d
[This](https://www.niddk.nih.gov/bwp) calculator yields similar results
So, pretty much in line with your conclusion.
If something is making fat cells want to expand more and give up fat less easily, a corresponding lack of glucose or triglycerides in the bloodstream will, obviously, cause people to eat more. Early studies in overfeeding before the obesity epidemic showed that you had to overfeed people a LOT to make them gain a small amount of weight, which was immediately lost after overfeeding stopped. This is how human metabolisms used to work, before something broke them.
Imagine somebody with cancer, maybe before surgery existed and people would just walk around with giant tumors. The tumor increases your weight. The metabolic input to increase the tumor has to come from somewhere. If you measure the food intake of the person with the tumor, they’ll probably eat more, maybe possibly exercise less, over that period. It doesn’t mean they can cure their cancer by eating moderately less in proportion to how much dietary intake increases when you have a tumor; eating less would make them hungry and less active, but wouldn’t shrink the tumor, which can just go on growing regardless.
People are getting fat, so they have to eat more.
Trust me, we’ve tried eating only untasty food. It’s not that.
I think saying “we” here dramatically over-indexes on personal observation. I’d bet that most overweight Americans have not only eaten untasty food for an extended period (say, longer than a month); and those that have, found that it sucked and stopped doing it. Only eating untasty food really sucks! For comparison, everyone knows that smoking is awful for your health, it’s expensive, leaves bad odors, and so on. And I’d bet that most smokers would find “never smoke again” easier and more pleasant (in the long run) than “never eat tasty food again”. Yet, the vast majority of smokers continue smoking:
https://news.gallup.com/poll/156833/one-five-adults-smoke-tied-time-low.aspx
A personal observation regarding eating not tasty food:
I served in the Israeli army, eating 3 meals a day on base. The food was perfectly edible… But that’s the best I can say about it. People noticeably ate less—eating exactly until they weren’t hungry and nothing more than that, and many lost a few kilos.
Adding my anecdote to everyone else’s: after learning about the palatability hypothesis, I resolved to eat only non-tasty food for a while, and lost 30 pounds over about four months (200 → 170). I’ve since relaxed my diet a little to include a little tasty food, and now (8 months after the start) have maintained that loss (even going down a little further).
What sorts of non-tasty food did you eat? I don’t really know what this should be expected to filter out.
For the first part of the experiment, mostly nuts, bananas, olives, and eggs. Later I added vegan sausages + condiments.
Slightly boggling at the idea that nuts and eggs aren’t tasty? And I completely lose the plot at “condiments”. Isn’t the whole point of condiments that they are tasty? What sort of definition of “tasty” are you going with?
Nuts, bananas and olives are tasty, and common snacking foods. What they are not is highly processed.
This sounds like a pretty intense restriction diet that also happens to be unpalatable. But the palatable foods hypothesis (as an explanation for the obesity epidemic) isn’t “our grandparents used to only eat beans and vegan sausages and now we eat a more palatable diet, hence obesity.” It’s something much more specific about the palatability of our modern 20th/21st century diet vs. the early 20th century diet, isn’t it? What’s the hypothesis we could test that would actually help us judge that claim without inadvertently removing most food groups and confounding everything?
I’ve heard that combinations of fat and sugar are particularly superstimulating.
I’m going to bury this a bit deeper in the comment chain because it’s no more indicative than Eliezer’s anecdote. But FWIW,
I am in the (very fortunate) minority who struggles to gain much weight, and has always been skinny. But when I have more tasty food around, especially if it’s prepared for me and just sitting there, I absolutely eat more, and manage to climb up from ~146 to ~148 or ~150 (pounds). It’s unimaginable that this effect isn’t true for me.
Yeah, that sounds right—with a non-broken metabolism, eating lots and lots of tasty food that’s just prepared and sitting there, to your heart’s content, should totally result in about 4 pounds of weight gain, all the way up to 150 pounds.
That’s how everybody’s metabolisms used to work.
Do you have any empirical evidence for either of the following?
Farmers were historically wrong to think that free-feeding their animals would tend to fatten them up, OR they didn’t believe it has that effect.
Prior to the more recent novel contaminants, humans are an exception among animals in this general trend, that free-feeding tends to fatten animals up.
Actually I’d ask about the effect of free-feeding non-domesticated animals on ecologically realistic food, rather than free-feeding cows bred to gain weight using grains.
Why “ecologically realistic food”? And which types of realism are you going to pick?
Overfeeding and obesity are common problems in pets, which are mostly not bred to gain weight the way cows are.
My family has kept many kinds of animals. If you give bunny rabbits as much veggies as they want, a large fraction becomes obese. And guinea pigs too. And for their own favorite foods, tropical fish do too. Cats too.
In fact, I have never noticed a species that doesn’t end up with a substantial fraction with obesity, if you go out of your way to prepare the most-compelling food to them, and then give that in limitless amounts. Even lower-quality, not-as-compelling foods free-fed can cause some obesity. Do you even know of any animal species like this?!
If there is large variation in susceptibility (which there would be) to the ostensible environmental contaminant, there should be species that you can free-feed and they don’t get obesity.
I agree that most animals will become overweight if given unlimited tasty food. Two counter examples in my life were a cat and a hamster. Both only became overweight in old age—with unlimited food and many treats. Caveat—the hamster didn’t look fatter than normal hamsters, but maybe all hamsters are fat.
Just adding my own anecdote here, literally every time that I can recall overeating out of my own volition, it was because the food was tasty or otherwise satisfying. The connection between how tasty a food is, and how likely I am to overeat it, is such a strong connection that it might as well be treated as a law of nature.
Doesn’t sound obviously true for me? I obviously won’t overeat food if it’s disgusting, but I’d say I’m more likely to overeat rice cakes than chocolate, for example. A lot of milder foods feel easier for me to overload on.
That’s interesting. One caveat I should add is that I was referring to calorie overconsumption, as opposed to volume overconsumption. Rice is not very calorie dense, making it relatively easy to become full without eating many calories.
Yeah, I was thinking of calories too. I think I could eat way too many rice cakes, reliably, day in and day out. Whereas eating even one Hershey’s bar starts to approach the level where I’d feel sick from the amount of chocolate, and want less of it around me in the future.
There’s more common foods everyone can agree are tasty and high calorie and easy to indulge on, such as spaghetti with meatballs
How are we defining tasty foods? I’m sure if the entire world voted, chocolate would clearly be more in the “tasty food” category than rice cakes, but perhaps you really like how rice cakes taste?
I think people are reading into my comment plenty of things that I didn’t say. My only actual claim is that the 20% increase in calorie intake is sufficient to “explain” or “account for” the increase in body mass from 1970 to 2010. It’s not small and the claim by SMTM that it’s small is inaccurate.
Your comment is about why people would be taking in more calories and I don’t think I have any special insight into that issue. I just don’t think SMTM has any special insight to it either. Your argument is obviously logically possible but I wouldn’t bet a lot of money that it would turn out to be the right explanation.
I’ll try rephrasing, somewhat overstating the strength of the reasoning (taking it from probabilistic to logical) in case that causes a basic idea to be clearly communicated that was obscured by probabilism.
If an increase in calorie intake was itself sufficient to produce an increase in fat mass in otherwise metabolically high-functioning adults, we’d have seen a different result from pre-obesity-epidemic experiments in overfeeding. This rules out the direction of causality “mere overeating” → “obesity”.
Any hypertrophy of fat cells, in turn, will causally require more nutritional intake to feed the hypertrophy, just like a cancer growing, or any other body part growing, will require more nutritional intake. So once you observe a cancer or a huge fat cell mass or any other diseased body part growing, you already know the person already took in that much food, both to grow the cancerous body part and sustain it; you shouldn’t be surprised to look back at the cancer patient’s caloric consumption record and find an excess; so finding that excess consumption shouldn’t update you at all about the cause of the malevolently growing body part.
You’re taking causality that must at least run from “fat cell hypertrophy” → “excess consumption” and already fully explains away the presence of an observed correlation, and then adding on a causal postulate that runs the other way—a direction of causality that would be theoretically possible in a world with no overfeeding experiments one way or the other, though not supported even there, since there is no otherwise unexpected observation which it explains; but which in our world is ruled out by the results of overfeeding experiments, which tested the results of experimental-intervention-produced excess calorie consumptions in metabolically healthy individuals before the obesity epidemic.
To further oversimplify the oversimplification: the logic you’re deploying for obesity would also work to conclude that overeating causes cancer, and therefore Proves Too Much.
The only reason why “overeating caused this huge fat mass to grow inside my body” sounds more plausible than “overeating caused this huge tumor to grow inside my body” is that the former theory follows the Sin Theory of Obesity in which obesity is a punishment for the sin of gluttony, while the latter theory is incongruent with simple just-world hypotheses as of the 21st century in Western societies. Both are ruled out by experiments showing that (in metabolically healthy individuals before the obesity epidemic) a randomized experimental intervention to add overeating does not produce obesity any more than it produces tumors.
I think the first sounds more plausible because the story “humans store caloric excess as fat in times of plenty and burn it off in times of scarcity” is the kind of thing that we should have as a hypothesis-under-consideration before we look at the link between calorie intake and body mass. Whereas “humans store caloric excess as cancer” (or as fetuses) isn’t. And if that story is true, then “eating lots of caloric excess causes lots of fat to be stored” isn’t automatically true, but again it’s definitely something we should have under consideration.
So if your line here is meant to be taken a priori—that is, if you’re saying “even without actually looking at the link between caloric intake and body mass, there’s no reason to believe overeating-causes-fat any more than you’d believe overeating-causes-cancer”, then it seems just wrong.
Maybe you meant it a posteriori? Something like “okay but overeating studies show that eating lots of caloric excess doesn’t by default cause lots of fat to be stored, so you no longer have a plausible explanation”?
But then at least two other reasons come to mind for why overeating-causes-fat might still seem more plausible than overeating-causes-cancer. One is that someone might not believe that studies show what you think they show. Another is that someone might just be bad at propagating updates. Currently, these both seem more likely to me than your “sin theory” theory.
I strongly disagree with this interpretation of those overfeeding studies. From what I can tell (though I couldn’t access every study SMTM cites), “overfeeding” is usually defined relative to the output of one of the typical BMR/TDEE estimation formulas given a person’s parameters, not based on actual measurement of a subject’s TDEE. Those formulas are fine for a baseline guess, but even the most accurate ones are going to be substantially off in either direction for a fair number of people! Some of the difference is unaccounted-for NEAT, some of it is differences in absorption efficiency, some of it is probably other factors we don’t understand yet. Given the known reality of interpersonal variation in what your actual calories in and out are relative to their naive estimates, some subjects not gaining weight while “overfeeding” is exactly what you’d expect to see.
A fun fact: my estimated “effective TDEE” is (averaged over months) pretty consistently around 3300 cal/day for the past 18 months—rarely more than +/- 100 cal/day off in either direction—whereas the best formula I could find (using my body fat %, as actually-measured by a DEXA scan) says it should be something more like 2600-2800 cal/day. This is based on weighing my body daily and recording the caloric intake from actually-everything I eat, almost always weighing food when necessary rather than coming up with estimates.
I think I understood what you’re saying the first time around and again I agree that your account of things is certainly possible, but even in your case the tumor or fat mass has to be sustained by calorie consumption from the outside. The increase in calorie intake we’ve seen is about the amount we would have expected if someone had just told us that people are 15% fatter on average without any increase in exertion or heat dissipation to compensate for that.
Another way to say this is that I’m just making a claim about the conditional expectation E[average body mass increase | average calorie consumption increase = 20%] and pointing out this expectation is not far off from the actual observed body mass increase we see. In that sense the increase in calorie intake can account for the increase in body mass in correlational terms. The question of why both of these variables went up, though, is difficult and their level is obviously not determined by this argument.
Externally, why people feel the need to keep eating until they become obese is not a question with a clear (to me) answer. It could be because there is some process that’s operating in the body that’s taking priority over other activities and hoarding a lot of the energy intake to produce fat cells, which I think is your story. However, it could also be that some part of the brain is malfunctioning and leading the lipostat to be poorly calibrated. It could also be that the food you’re eating messes with the natural feedback loops in your body that are supposed to make you feel full when you’ve eaten enough.
I think this question is interesting and your account is logically possible. I just think that
I don’t have any special insight into which account is right, and
I don’t think your particular explanation is favored that much over other competing explanations.
I don’t think the overfeeding experiments provide strong evidence for your scenario, though I agree that they should be a Bayesian update in favor of accounts in that broad neighborhood. What would convince me is experiments which involve smaller increases in calorie intake but sustained over much longer periods of time, on the order of a year or so. If such experiments failed to find an effect that would be a strong update for me towards your view. Right now I buy the cancer analogy on conceptual grounds but I don’t think we have enough evidence to conclude obesity is like cancer in this regard, though it very well could be the case.
To give an analogy of my own, the overfeeding studies look similar to attempts to settle disputes about which programming languages are best for productivity by asking undergraduates to complete some simple tasks in them over the course of a few weeks. What really matters is how you do when you’re working with big and complex software in the real world that has to be developed and maintained by large teams with turnover for years, sometimes decades; but that obviously doesn’t lend itself to a simple experimental design so people still keep arguing about it.
Retrying again:
By the same reasoning:
“Pregnancy” probably isn’t a thing. “Pregnant” people eat around 500 more calories per day. This is sufficient to explain all the weight gain from “pregnancy” without supposing anything other than thermodynamics at work—anyone who eats an extra 500 calories per day will probably gain that much weight over the course of 40 weeks.
I think Ege’s alleging that SMTM presented two causal graphs:
calories → ? → weight gain
calories → weight gain
Ege’s saying that 2 is simpler and sufficient, so we don’t need to posit a ? in the middle.
You’re pointing out that we still need to address a third causal graph:
? → calories → weight gain
Edit: And maybe that there’s also a scenario where ?, calorie intake, and weight gain are all in some complex interrelationship. Maybe contaminants cause more fat deposition and less energy and more hunger, thereby increasing weight gain per calorie, increased calorie intake, and increased contaminant intake via food. Or something.
Ege’s agreeing with you, but wants to emphasize that this is compatible with criticism of SMTM’s alleged emphasis on graph 1.
Note: I say “alleged” only because I’m sidestepping evaluating the truth of Ege’s claim. Just trying to clarify what it is (AFAICT).
I don’t agree with this presentation of what I’m saying.
I’m not terribly sure what SMTM means when they say “the increase in calorie intake is small”, but all possible interpretations of their claim seem wrong. For instance, one plausible interpretation in causal graph lingo is “if you applied the do operator on calorie intake and raised it by 20%, we would have seen an increase in body mass that’s significantly smaller than what we’ve actually seen”. I think this claim is wrong, basically for long-run energy balance reasons.
I’m not saying anything else about the structure of the causal graphs, which could be arbitrarily complicated and involve arbitrarily many nodes and dependencies. I’m just saying that if you apply the do operator on calorie intake and raise it by 20% then you’d get an increase in mean body mass that’s about as big as what we’ve seen.
Thanks for clarifying that I misrepresented your view. Based on your response here, you’re pointing out that there’s a strong correlation between increased caloric intake at the population level, and increased obesity. You are also saying that the explanations you’ve read from SMTM for why this correlation exists seem wrong, and also that they underestimate the magnitude or importance of the caloric intake.
WRT Eliezer’s arguments, you seem to be agreeing that there may be some underlying force(s) causing that increased caloric intake. However, you are very uncertain about which, if any, of the hypothesized forces(s) are the true causes of increased caloric intake.
Eliezer and others seem to be perhaps mistakenly interpreting you as denying the existence of, or “need for,” a deeper explanation for increased caloric intake and consequent weight gain. You are confused about why they are making this mistake.
Is that a more accurate account of your position?
Yes, this summary is accurate.
I’m not sure who is “to blame” for the miscommunication but I suspect I simply was not clear enough in my top comment. Now it’s likely too late to clear up the issue for most readers as they won’t be following the developments in this thread.
Feel free to adapt, or copy/paste, the summary into your parent comment if you like.
This is “assuming there’s no link “increased calorie intake → increased energy expenditure”″, right? I think one of the things Eliezer is saying is that there seems to have been such a link in the past and now there isn’t / it’s much weaker.
That’s not quite true—there is at least the naive link that a higher equilibrium body mass leads you to expend more energy in daily activities even if you exercise the same amount as before. In my very naive model I assume these are directly proportional, but Natalia cites some better research that does a log-linear regression of calorie expenditure on equilibrium (I think? I didn’t check this part) body mass which seems to be more accurate empirically.
I think it’s unclear whether we had the link you mention in the past, too. We definitely had a correlational link: people who did hard labor and ended up exercising a lot every day took in much more calories, as we would expect, and they were generally not obese. However, I think my argument would work just as well in the past if you just applied the do operator on calorie intake per day and looked at the causal impact on equilibrium body mass, as I don’t think there’s evidence that there’s a big downstream link from calorie intake per day to exercise.
You left out weight gain->calories, as in the pregnancy example, and calories ← X → weight gain.
I don’t understand why you’re “retrying”. I already agree with your point and you not saying “yes, you already agree with me” is quite confusing to me. As I say in my comment:
Do you think this characterization of your position is unfair or wrong? If so, why?
As far as I can see the only object-level point I disagree with you about is that I don’t think the evidence for obesity being like cancer or pregnancy is as strong as you seem to think it is. It’s definitely possible for it to be like that but I would bet against it at even odds. I explain this here:
On top of that I also have a separate disagreement with you about emphasis in the context of my comment, since the point of my top comment is to draw attention to 400 kcal/day not being a small increase in calorie intake. You agree with me about this but you just don’t think it’s worth focusing on, probably because you think it’s a trivial observation. I still think it’s something that should be corrected given that SMTM explicitly said that it’s a small increase.
Some people certainly are obese because of literal cancer and literal pregnancy. We seem to have strong evidence for that.
The interesting question is about how much of the obesity pandemic is explainable by such factors and not whether evidence for such factors exists.
We certainly don’t see enough pregnancy and cancer to explain the obesity epidemic but there might be other factors that are similar but harder to see. Thermodynamic arguments don’t help us rule out other effects that are similar to pregnancy/cancer.
I agree with everything you said, so again I’m confused why you thought you should make this comment.
I feel like I don’t really disagree with most of the commenters but they either think I do disagree with them or that I did a very bad job of communicating exactly what my point was. It’s hard for me to understand.
(The thread continues to look to me like what I described here https://www.lesswrong.com/posts/7iAABhWpcGeP5e6SB/it-s-probably-not-lithium?commentId=NxzEfuyGfuao25mrx
i.e. Yudkowsky is responding to the part of your original comment where you said
)
I still stand by this claim, again with the caveat that you take it as a correlational use of the word “explain” (which is not at all uncommon e.g. when talking about “fraction of explained variance” and so forth) and not one that suggests a causal explanation of the form “people wanted to eat more food, so they ate more food, so they got fatter as a result”.
Ok. My main point is just to clarify that other people are reading you as talking about explanation in general, not just strictly correlational explanation (if that’s what’s happening).
I do also think that’s not a great use of the word “explain” and “mystery”, because it’s not why the colloquial word is useful. The colloquial words “explain”/”mystery” are useful because they index “more information and ideas given/needed about this”. So just because X correlationally explains Y, and X is true, doesn’t mean there’s no mystery about Y.
I never said there’s no mystery about Y, just that there’s no mystery about Y being true conditional on X being true.
It’s a fair point that my usage of “explain” and “mystery” confused some people but I’m not too sure how else I would have made my point. Should I have said “people today are eating about as much more compared to the past as we would expect given how much fatter they’ve gotten”?
That’s clearer to me, yeah. It’s unambiguous that it’s about conditional prediction (“we would expect given”) rather than explanation-in-general.
In your original comment, you wrote:
Read literally, this says: There’s a mystery of why intake went up. Conditioned on intake up, there’s no mystery of why fat went up. I think this isn’t right. If we agreed that sustained high intake implies weight increase, it’s still not right. That’s because conditional probability isn’t the same as explanation, and if there’s a mystery, what we’re after is explanation. That’s one of the points of the tumor example: If fat causes intake, then saying “there’s no mystery about fat” is pointing away from the explanation of intake, which is that fat causes intake and something causes fat.
Taken literally, this seems to be consistent with beliefs of people who disagree with you? It’s just that they have different conclusions about the causality going through calorie intake. Interpreted that way, I don’t see how this statement is consistent with saying “there’s really no mystery in Americans getting fatter”.
I don’t understand your objection. I never made any claims about causality. My whole argument is about energy balance, which says nothing about causality.
On the other hand, I think it’s just true that conditioned on the increase in calorie intake there’s no mystery in the increase in body mass. I don’t understand why you’re disputing this point. You can say this is not an interesting observation (which I agree with, though as far as I can tell SMTM did not, which is why I wrote my comment) but I don’t see how you can say it’s not right.
My impression is that some people are engaging in a bizarre combination of steelmanning SMTM’s point while strawmanning my own. SMTM didn’t make the best version of the claim they could have made, they made the actual claim that I quote in my post. I think their claim is wrong. Do you disagree with this or not?
Meta: my interest here is to see if there are miscommunications here that I can clear up. I’m not carefully following the object-level debate. (In particular, I think that you Ege should feel extremely free to ignore what I’m saying as unhelpful to you; if I’m not helping you understand what’s happening in the thread then I’m not doing what I’m trying to do.)
(Note: you did mention causality in the passage I quoted: “They should have been focusing on the causal channel going through calorie intake from the start.” That’s not a claim about what causes what, but it is a claim about what questions are the right questions to ask.)
I’m pointing at the word “mystery”. I’m saying that to me, “mystery” means “explanation wanted”. I’m saying that just because P(X|Y) is high, doesn’t mean Y is a good explanation of X. (For a silly example, setting Y=”X and 2+1=3″ makes P(X|Y) = 1 and is obviously doesn’t explain anything.) I agree (based on my preconceptions, ~0 independent data) that P(body mass high | high sustained intake in the wild) is high. My read of some of the comments on your comment, e.g. Yudkowsky’s, is that they are taking you to be saying “high intake explains fat, such that there is no further interesting question about fat, though there may be further questions about why high intake”, based on the passages from your comment I quoted. Reading your comment closely, you didn’t actually say that, if by “conditional on Y, there’s no mystery about X” you mean “P(X|Y) is high”. In fact, what you said is consistent with believing that “Alice is fat” explains (in the contextually relevant sense) that “Alice has high intake”, and you recommend that if you believe this then you should “focus[] on the causal channel going through calorie intake”, i.e. investigate why Alice is fat in order to explain her high intake.
I don’t know. I think your argument makes sense, but the actual situation is going to be more complicated.
Do you know, if we also observe an obesity-epidemic in the subgroup of people who average 25k+ in daily steps? That step-requirement is a good, high standard of “metabolically healthy” to isolate.
I belong in that group these days and it feels natural, relaxed and I feel far more energetic than when I was averaging 7k daily steps and was the sedentary nerd cliché, about a year ago. Now I am a nerd, who takes two walks per day, almost never sits and either stands or uses his office treadmill when on the computer.
Even before, I never really got fat. But I feel, that I might not have been “metabolically healthy”, because now I feel better. So I strongly suspect that a far higher than average step-count is a hard requirement for being “metabolically healthy”.
I hear that “pregnant” people also do less mountain-climbing, even if they were exercising healthily before. No wonder they gain weight! Do we even need to postulate “pregnancy” as a condition, when their caloric intake and reduced exercise seems adequate to explain all of the observed weight gain?
I was not responding to your pregnancy-argument, but to your post higher up in this subthread from 3 days ago. The threading makes this a bit confusing.
Also should have specified what I was responding to the last paragraph:
”Both are ruled out by experiments showing that (in metabolically healthy individuals before the obesity epidemic) a randomized experimental intervention to add overeating does not produce obesity any more than it produces tumors.”
Is there actually an obesity epidemic among people who walk more than 25k steps per day? (or is something like that currently known).
EDIT:
I suppose my hypothesis is:
Living a non-sedentary lifestyle meaning less than 20 minutes of sitting per day, 25k-ish steps per day somewhat equally spread out over all waking hours makes the “weight-gain -=> obesity”-phenomenon impossible, because it’s a sufficient requirement for robust metabological health.
If that was true, it might not answer what is behind the obesity epidemic.
But that’s what I would study, to check if it’s a cure or reliable prevention.
I’d say 90% chance of this being true, but mostly on intuition and with high model uncertainty.
And I don’t know, if we know enough to answer this question, because non-sedentary lifestyles like that are fairly niche in all Western societies. But I recently figured out, that they’re not all that hard to adopt.
EDID2: Actually, I’d say the 90% applies to it being “reliable prevention”. No clue, how curative that would be.
I never had to really lose more than a couple kg of fat. [and “had to” is really exaggerating a lot]
From what I observe, it seems somehow impossible for really fat people to become not fat, despite heroic struggles which have always been strange to observe from the outside.
Is there any solid evidence that walking 25k steps per day will solve the obesity epidemic? I ask this because it’s genuinely a remarkable claim, one that if verified and implemented would save huge numbers of lives and hundreds of billions in medical expenses. The literature mostly seems to indicate that increased exercise doesn’t have dramatic effects on obesity.
There is not. That’s why I was asking him if he knows. I was not interested in the effect of exercise. Exercise means, you do some activity a couple times per week.
I’m interested whether the obesety epidemic only affects the sedentary populatrion.
And if being or becoming non-sedentary is protective or curative.
25k steps for me means, that my treadmill is running constantly when I’m on my computer.
This is not really exercise. Movement is just my default state.
In that way, I have become closer to what an EAA-hunter-gatherer, than to a sedentary office worker does with his body.
[or I would, if this had been my lifetime norm instead of something I still get used to]
If the human body was sold as a machine, the sedentary lifestyle probably would void your warranty, because it’s rather extreme (dis)usage. Sedentary people being unhealthy is not surprising.
It’s surprising that some sedentary people aren’t.
Anyway, “being in near-constant motion” is too specific/complicated a metric.
So I’d just look for a step count high enough, that’s only feasibly doable by a non-sedentary person like me. Though, I guess any daily jogger can probably match or exceed 25k steps per day.
The group of people whose 80th quantile waking hour still has >1k steps.
That’s probably the better proxy, come to think of it.
All right, here’s my crack at steelmanning the Sin of Gluttony theory of the obesity epidemic. Epistemic status: armchair speculation.
We want to explain how it could be that in the present, abundant hyperpalatable food is making us obese, but in the past that was not so to nearly the same extent, even though conditions of abundant hyperpalatable food were not unheard of, especially among the upper classes. Perhaps the difference is that, today, abundant hyperpalatable food is available to a greater extent than ever before to people in poor health.
In the past, food cultivation and preparation were much more labor intensive than in the present, so you either had to pay a much higher price for your hyperpalatable food, or put in the labor yourself. Furthermore, there were fewer opportunities to make the necessary income from sedentary work, and there wasn’t much of a welfare state. Thus, if you were in poor health, you were much more likely in the past than today to be selected out of the class of people who had access to abundant hyperpalatable food. Obesity is known to be a downstream effect of various other health problems, but only if you are capable of consuming enough calories, and have access to food that you want to overeat.
Furthermore, it is plausible that some people, due to genetics or whatever, have a tendency to be in good health when they lack access to abundant hyperpalatable food, and to become obese and thus unhealthy when they have access to abundant hyperpalatable food. Thus there is a feedback loop where being healthier makes you more productive, which makes hyperpalatable food more available to you, which makes you less healthy, which makes you less productive, which makes hyperpalatable food less available to you. Plausibly, in the past, this process tended towards an equilibrium at a much lower level of obesity than it does today, because of today’s greater availability of hyperpalatable food to people in poor health.
It is also plausible that our technological civilization has simply made considerable progress in the development of ever more potent gustatory superstimuli over the past century. This is a complex optimization problem, and it’s not clear why we should have come close to a ceiling on it long before the present, or why just contemplating the subjective palatability of past versus present-day food would give us conscious awareness of why we are more prone to overeating the latter.
Both of these proposed causes are consistent with pre-obesity-epidemic overfeeding studies of metabolically healthy individuals failing to cause large, long-term weight gain: They suggest that the obesity epidemic is concentrated among metabolically unhealthy people who in the past simply couldn’t afford to get fat, and that present-day food is importantly different.
Adderall works.
Adderall worked for you. It didn’t work for me.
What was it that eventually did work for you?
Adderall caused weight gain for me, and anecdotally also for a close friend of mine. Wellbutrin works, though, at least for me personally.
Lots of drugs have effects that vary wildly between different individuals (and they may even sometimes cause paradoxical effects), so I’m not sure that variance in response to amphetamines is necessarily that much of a hint about what is causing the obesity epidemic. If semaglutide works universally, or nearly so—and early studies are very promising—then that might be a strong hint as to what is causing the obesity epidemic.
Relatedly, this seems to be the distribution of weight changes on 15 mg of tirzepatide + lifestyle interventions, compared to lifestyle interventions alone (over 72 weeks, I think):
This guy says it’s fructose, plus salt and MSG. “Nature puts a “survival switch” in our bodies to protect us from starvation. Stuck in the “on” position, it’s the hidden source of weight gain, heart disease, and many other common health struggles. But you can turn it off.” I think he’s on to something; since I’ve been following his recommendations, I’ve been able to lose weight again ( ~9 kg since the end of April).
I feel like you’ve missed SMTM’s central point. Sure, people are eating more. The main question is why people eat more. For example, I used to weigh 172 pounds in the Philippines 4 years ago; now I weigh about 192 in Canada. I used to think my overweight best friend was overfeeding me (well, he did), but since he moved away two years ago, I’ve actually gained weight somehow. I have a mild sense of being hungrier here. Presumably I am eating more, but why?
(Having said that, it looks like OP has done great work and this is a big red flag:)
This isn’t the core of why I think you think that’s a red flag, but for the record I don’t think a week is that much time to respond to public criticism. I have many important emails I don’t reply to for longer.
FWIW, the first time I contacted them about those studies was 15 days before the publication of this post.
I was thinking about comment approval more than response [and to make that clearer, I appended to my quotation above]. I’ve been perma-declined myself, not fun. Unfortunately if it’s approved now there will be a question as to whether it was approved now in response to an ultra-popular LW post.
I didn’t downvote you, I think you are eloquently arguing your point here! But I’m not entirely sure that the SMTM take is quite as bad as you make it out to be.
An average of 400 extra calories a day isn’t small on its own, but I think the SMTM argument is that it’s small compared to historical variation in caloric intake, and small compared to variation among humans in general today. In other words: there were likely times and cultures historically where average calories consumed was higher or lower than today by more than 400 calories—why wasn’t there an obesity epidemic previously when caloric intake was higher? Why, 100 years ago, were not the people eating 400 extra calories a day all obese?
I clearly found it more a more compelling argument that you do. Like you, I read the SMTM contaminant argument as essentially saying “historically there has been some process that kept calories consumed and calories expended in relative sync; that process has been disrupted”—and the argument that “400 calories per day explains the weight gain” isn’t really a counterargument to this?
I’ll point out one more aspect that I think you may want to consider. You write: “to me it’s quite obvious that in the long run more calorie intake has to lead to higher body mass”—but this is a statement that is somewhat circularly derived from today’s observations. 100 years ago, when very few people were obese, this statement might not be obvious at all. One might instead conclude that people with higher calorie intakes are compelled to burn more calories through manual labor, exercise, heat generation + sweating, etc.
Lastly, and obviously you know this on some level, but the fact that increased food consumption correlates with obesity, does not imply that that consumption causes obesity. SMTM argue that some external factor causes obesity; if so, increased food consumption would be a result of the body trying to maintain that weight. As you note, a 15% increase in body mass requires a 20% increase in caloric intake to sustain—if an external factor is increasing the lipostat, we would observe exactly what we observe today as well. It’s dangerous to point the causal arrow in either direction without more evidence.
And, speaking of evidence: the overfeeding studies are interesting in part because they at least resolve the question of whether and how much short-term overeating causes body mass increases; you’re 100% correct that they don’t resolve the question of whether long-term overeating also causes body mass increases, and it would be super interesting to see if a long-term (say, 1 year) 400-calorie increase in consumption (that somehow doesn’t come from changes in diet; maybe just eat an extra 20% at every meal?) causes weight gain.
As far as I know, no one’s run a long-term weight gain study—but we do have the super confusing result that a 30-40% decrease in calories is hard to sustain and the resulting weight loss plateaus at about a 10% decrease [0], suggesting that there’s more going on than the simple linear relation.
[0] https://www.nejm.org/doi/full/10.1056/NEJMoa2114833
Variation among humans can be caused by variation in their metabolism (or variation in how much they exercise) that changes the amount of energy they expend per unit mass without being inconsistent with the energy balance argument. There’s a lot of place variation in the cross section can come from other than calories consumed—I don’t think that’s actually that relevant to understanding trends in obesity. Energy balance can hold at any level of calorie intake so the question is why you settle on one point of equilibrium and not all the others, given that you’re the one making the decisions about how much to eat.
As for historical data, I’m not convinced there’s ever been a time when mean calorie intake in a reasonably large country was ever as high as it is in the US today. There’s of course been plenty of variation but I’d expect the variation to show up in body mass if it were sustained.
I’m not really convinced by the claim that what’s happening now is historically unprecedented and I think most of the work there is being done by summarizing the phenomenon in terms of obesity statistics instead of mean body mass. I think if we looked at the historical trajectory of mean body mass it would not really look like anything exceptional is happening today in terms of some fundamental balance process being thrown off.
I want to repeat: the point of my comment is not that “why are people eating more now?” is a question that shouldn’t be answered; it’s that the claim about 400 kcal being too small of an increase is just wrong. If you agree with that then you should just agree with my comment because that’s the only claim I make.
I think my argument says nothing about how hard to sustain a decrease in calorie intake is—it’s consistent with your body making arbitrarily strong protests at having to burn its stores of fat and try to induce you to eat more to compensate. I’m agnostic on that point and I think it’s obviously an interesting question to look into.
Farm laborers historically ate a lot of calories just to be able to get through their days. Their calories weren’t very appetizing, but they had to eat a lot because they burned a lot.
That makes sense to me but I’d really need to see the data on how many calories they ate in 1700. I notice I would still be surprised if an average farm laborer in 1700 in prime age ate more than 2400 kcal/day. It’s not really relevant to my main point but if you have some data proving that I would be interested to see it.
Per Jeffrey L. Singman, Daily Life in Medieval Europe, Westport, Connecticut: Greenwood Press, 1999, P. 54 − 55 (and text copied from https://stores.renstore.com/food-and-drink/dietary-requirements-of-a-medieval-peasant), “A prosperous English peasant in the 14th century would probably consume 2 − 3 pounds of [rye, oats, or barley] bread, 8 ounces of meat or fish or other protein and 2 − 3 pints of ale per day”, which works out to about 3500 to 5000 calories per day.
That same page lists various farm chores as burning 1500-7500 calories over an 8 hour period, so assuming some mix of those plus the normal base calorie burning easily adds up to over 3500 calories.
This blog post (https://www.worldturndupsidedown.com/2011/08/how-many-calories-did-they-eat-in-day.html?m=1) looked at a shopping list from the 1860s and found that men ate about 3500 calories per day while women ate about 2500 calories per day. I’m not sure what audience this was aimed at (farmers? factory workers?) but clearly it’s more than 2400 calories per day.
This post (https://oureverydaylife.com/321257-the-peasant-diet.html) cites “research published at Eastern Kentucky University” to say that “an average medieval person burned between 4,000 and 5,000 calories per day … A typical diet for peasants delivered between 3,500 and 4,500 calories, about or just under the need.”
If you’d like I can do more academic research, but these independent sources all roughly corroborate each other so I’m personally satisfied.
One note is that the food eaten historically was much less appealing to eat. I don’t think they were eating 3 pounds of bread because they really liked oat bread, but rather that they needed it to survive doing hard manual labor for 8 hours a day.
Thanks, that’s interesting. Intuitively I would not have expected them to be burning so many calories.
Reported numbers vary quite a bit (perhaps in part because the physical activity intensity of training or warfighting also varies), but you might be interested to know that soldiers in training or active duty might hit something like 4000-5000 kcal/day in energy expenditure, maybe thousands more for outlier people and/or circumstances.
How much did city dwellers in the early 20th century eat? There must have been a period when people were not doing so much manual labor but before the obesity epidemic.
A lot of city dwellers then were doing manual labor (factory lines, construction), but I’m really not sure about the office workers from them. It’s a good question!
I think you are missing my point—which EY also makes above—that you are concluding that the calorie consumption increase causes obesity when in fact none of the evidence you provide supports pointing the causal arrow in that direction specifically.
We know obese people eat more, and we know that the greater fat mass has greater nutritional requirements.
The interesting question is not whether 400 calories are associated with the weight gain, clearly people are more obese now and also they eat 400 more calories on average, no one is disputing this. The interesting question is whether those 400 calories cause the weight gain or are caused by the weight gain. You are implying the former but there is not a lot of evidence in support of it—and other posters in this thread are chiming in with other evidence suggesting that 400 calories daily is well within normal historical variation, which is SMTM’s point that “400 extra calories causes weight gain” would be weird.
No I’m not. I don’t understand why people are jumping to this conclusion—I said several times that “the only claim I’m making is X” but people keep attributing to me claims that are not X.
As I’ll repeat here again, the whole point of my comment is to question SMTM’s claim that a 20% increase in calorie intake is small. It’s not small. I agree otherwise that the interesting question is what caused people to shift from one equilibrium to another and talking about energy balance doesn’t help clear up that point. It’s just not the point I’m trying to make, though.
I think we are getting caught up in the definition of “small”. My original point earlier is that 400 calories is small compared with historical variation and variation among humans. Your original point is that 400 calories is more than enough to explain the weight gain and thus isn’t “small”. Those are different definitions of small, and are both true: 400 calories is small compared with historical and present variation among humans AND 400 calories is enough to explain the extra weight.
But the latter is obvious; clearly those 400 calories explain the weight gain, because people aren’t suddenly metabolizing air or water or other calorie-free inputs into extra weight, those fat cells are creating fat from calories people consume. I suspect people are ascribing other claims to you because “400 calories is not small—it’s enough to explain the excess weight” is only a useful claim in this context (“this context” being “what causes obesity?”) if you are also making the causative claim.
You insist you are not making the causative claim—so what exactly are you arguing re: the question of “what’s causing the weight gain?”
I mean, obviously the causal chain of weight gain is often going to go through caloric intake, but that doesn’t make caloric intake the root cause. For example, birth control pills, stress, and soda machines in schools all cause weight gain via increased caloric intake, but are distinct root causes.
As I said in my original comment, this might seem obvious to you but unfortunately it’s not obvious to everyone. In addition, it’s also not necessarily correct: you can get fatter because you expend less energy too. I think empirically it seems like just looking at calorie intake and assuming the energy expenditures are fairly flat is a decent story but that’s definitely not a conclusion you can reach a priori.
I wonder if the macronutrient rates shifted. This would influence the total calories you end up with because absorption rates are different for different macronutrients. How the food is processed also influences absorption (as well as the total amount of calories that may not be reflected on the package).
If these factors changed, calories today don’t mean exactly the same thing as calories in 1970.
Since FDA allows a substantial margin of error for calories, maybe producers also developed a bias that allows them to stay within this margin of error but show fewer calories on the package?
Maybe this is all controlled for in studies, dunno, I just did a couple of google searches and had these questions.
I have no clue about this, unfortunately.
With +305 karma at the time of this writing the post has a very high karma count. If you look through recent post the only posts with higher karma are AI risk posts written by very senior people (Eliezer and
Paul Christiano).
Without an easy way to look it up it wouldn’t surprise me if +305 karma puts the post in the top 20 posts by karma that exists on LessWrong2.0.
Ege Erdil was referring to a flurry of downvotes that this post got within ~30 minutes of being posted. I don’t remember the exact number, but at the time he made that edit the karma count was quite low due to them.
When I made the edit this was not the case and the post was getting quite a lot of downvotes. Apologies for not including a timestamp. It was like 30 minutes to 1 hour after the post had been published and at some point I think the post had more people that had voted on it than it had net karma with a couple of strong upvotes that I knew had been thrown into the mix, including my own.
I’ve downvoted this comment; in light of your edit, I’ll explain why. Basically, I think it’s technically true but unhelpful.
There is indeed “no mystery in Americans getting fatter if we condition on the trajectory of mean calorie intake”, but that’s a very silly thing to condition on. I think your comment reads as if you think it’s a reasonable thing to condition on.
I see in your comments downthread that you don’t actually intend to take the ‘increased calorie intake is the root cause’ position. All I can say is that in my subjective judgement, this comment really sounds like you are taking that position and is therefore a bad comment.
(And I actually gave it an agreement upvote because I think it’s all technically true)
I think the people who believe my comment is unhelpful aren’t understanding that the content in it that seems obvious to them is not obvious to everyone.