I’m very skeptical of reasoning like “it was like that in ancestral environment so it must be good”. There are at least three reasons that makes me uncomfortable with the reasoning :
Even if we consider evolution to be a perfect optimizer (which it is not), there is a huge difference between “our digestion system is optimized to make the best possible use of food X” and “food X is best possible food for our digestion system”. If you made an algorithm A optimized to transmit data on a noisy channel N, it doesn’t mean the algorithm wouldn’t run better on a less noisy channel C. There may be an algorithm B that work better on the clear channel C than A, but still, A can work better on C than on N.
Evolution doesn’t optimize for the same purpose we do. Evolution doesn’t optimize for us to live long, it has a very low pressure to make us live past ~60, for example.
We have completely different lifestyles and activities than we did during paleolithic. And the optimal diet very likely depends of lifestyle and activities.
That said, what would convince me to do a diet is not a plausible-sounding reasoning, but some evidence of short-term and long-term effects on a sane sample size, with a control group. Something which seems very rare in the diet field, saddly.
Your grounds for skepticism match the heuristic that Anders Sandberg and Nick Bostrom propose in The wisdom of nature quite closely. They propose this heuristic to evaluate interventions to enhance humans, but it’s clear that it has much broader applicability. Here’s the relevant excerpt:
Suppose that we liken evolution to a surpassingly great engineer. (The limitations of this metaphor are part of what makes it useful for our purposes.) Using this metaphor, the EOC can be expressed as the question, ‘‘How could we realistically hope to improve on evolution’s work?’’ We propose that there are three main categories of possible answers, which can be summarized as follows:
• Changed tradeoffs. Evolution ‘‘designed’’ the system for operation in one type of environment, but now we wish to deploy it in a very different type of environment. It is not surprising, then, that we might be able to modify the system better to meet the demands imposed on it by the new environment. Making such modifications need not require engineering skills on a par with those of evolution: consider that it is much harder to design and build a car from scratch than it is to fit an existing car with a new set of wheels or make some other tweaks to improve functioning in some particular setting, such as icy roads. Similarly, the human organism, whilst initially ‘‘designed’’ for operation as a hunter-gatherer on the African savannah, must now function in the modern world. We may well be capable of making
some enhancing tweaks and adjustments to the new environment even though our engineering talent does not remotely approach that of evolution.
• Value discordance There is a discrepancy between the standards by which evolution measured the quality of her work, and the standards that we wish to apply. Even if evolution had managed to build the finest reproduction-and-survival machine imaginable, we may still have reason to change it because what we value is not primarily to
be maximally effective inclusive-fitness optimizers. This discordance in objectives is an important source of answers to the EOC. It is not surprising that we can modify a system better to meet our goals, if these goals differ substantially from the ones that (metaphorically might be seen as having) guided evolution in designing the system the way she did. Again, this explanation does not presuppose that our engineering talent exceeds evolution’s. Compare the case to that
of a mediocre technician, who would never be able to design a car, let alone a good one; but who may well be capable of converting the latest BMW model into a crude rain-collecting device, thereby enhancing the system’s functionality as a water collecting device.
• Evolutionary restrictions. We have access to various tools, materials, and techniques that were unavailable to evolution. Even if our engineering talent is far inferior to evolution’s, we may nevertheless be able to achieve certain things that stumped evolution, thanks to these novel aids. We should be cautious in invoking this explanation, for evolution often managed to achieve with primitive means what we are unable to do with state-of-the-art technology. But in some cases one can show that it is practically impossible to create a certain feature without some particular tool—no matter how ingenious the engineer—while the same feature can be achieved by any dimwit given access to the right tool. In these special cases we might be able to overcome evolutionary restrictions.
But it’s really slow, some new traits are lactas in adult age, gluten tolerance, but rerouting your entire metabolism is something altogether. Besides optimising from evolutions point of view (e.i. maximise reproduction) is not the same as optimising from most peoples point of view (e.g. living longer, being healthy past middle age).
Evolution doesn’t optimize for the same purpose we do. Evolution doesn’t optimize for us to live long, it has a very low pressure to make us live past ~60, for example.
Most living people don’t optimise for that either. If they did, more would practice calorie restriction.
I’ve yet to see any evidence on the effects of calorie restriction on humans. Mice are quite different from us, and all evidence on calorie restriction I’ve seen was done on mice.
Also, there is no just how long you live, but also life quality. We know the brain is a massive consumer of calories. We know that when people are even in light hypoglycemia, their reflexes and cognitive abilities go down. I never saw any study on the effects of calorie restriction to attention, reflexes and cognitive abilities.
I’ve yet to see any evidence on the effects of calorie restriction on humans. Mice are quite different from us, and all evidence on calorie restriction I’ve seen was done on mice.
I’ve yet to see any evidence on the effects of calorie restriction on humans. Mice are quite different from us, and all evidence on calorie restriction I’ve seen was done on mice.
Evidence on humans can be found through here, and extensive discussion on evidence in macaques can be found here (although I recommend reading the whole discussion and/or the study; the root comments are less informed than the leaf comments).
I believe there have been encouraging experimental results in other mammals, including primates, as well as human trials with surrogate endpoints. I also recall seeing a least one ongoing prospective cohort study with promising interim results. Will google and append links when I get a moment.
I would expect mild ketosis to compensate for hypoglycemia, but cognitive effects are of concern to me as well. Anecdotally, while practicing intermittent fasting regularly I did not appear to suffer any cognitive impairment.
I do feel (but yes, that’s error-prone) that I’ve lower concentration/thinking ability when I’m late for a meal.
Also, my parents (both retired teachers, one at uni the other in secondary school) both noticed that pupils/students were less focused and more error-prone in the hour just before lunch, and AFAIK (but I’ve no link right now to point at) this was backed by more formal studies than just “personal experience”.
There is also a certified increase of rate of car accidents in Muslim countries during the Ramadan month, due to lower attention/reflex speed when people are doing Ramadan, but AFAIK it’s unsure how much is because of hypoglycemia and how much is because of dehydration.
Edit : for my own personal experience, it may also be because I’m on the skinny part of the spectrum, I weight ~55kg for 170cm, so I get hypoglycemia quite fast if I don’t feed enough or regularly, it may very well be different for people who have more reserves than I do.
I do feel (but yes, that’s error-prone) that I’ve lower concentration/thinking ability when I’m late for a meal.
Being late for a meal is very different than restricting calories. If you eat a meal at the same time every day, your body gets in the habit of wanting to digest food at that point in the day. More blood re-routed to digestive system, less blood to the brain --> lower concentration/thinking ability before meal. Note I am partially pulling this out of my ass.
I feel better when coming back from lunch, so it’s not the “re-routing blood to the digestive system”. But it could be something with sugar level management, yes, my body expecting to be fed at 1pm, so not taking the expense to start using stocks to provide me with sugar when we are near that time, instead waiting for the coming meal, or something like that.
Anyway, I more wanted to say that diet/calories issues aren’t simple, and that “rodents live 20% longer when on calorie restriction in a lab” is just weak evidence that it would be good for us to do so. There are many aspects to consider (differences between men and rodents, effects on intellectual abilities or overall well-being, immune system strength, capacity to recover in case of disease/wound, effects on different ages, sex or corpulence, …) and studies that evaluate all of that are lacking.
Maybe calorie restriction is worth it, but there is just not enough evidence to tell. Saying “Most living people don’t optimise for that either. If they did, more would practice calorie restriction.” seems to me broad overconfidence.
In sensible CR experiments (which date back to the 1950s) the control mice are calorie restricted too, precisely in order to rule this possibility out.
It could be, yes. One question I have here is what is ‘morbidly obese’? Is it like IQ, where it’s essentially a relative ranking (the top fifth is the fattest and defined as morbidly obese), or do we have a clear bright line from biology where a certain weight is the crossing point between good and bad? If it is the former, then for all we know, Okinawans who were eating their fill were still above the bright line even though they look thin and fit from a contemporary American viewpoint.
Yes. My grandmother seems to not give a damn about how much longer she’s going to live, only about how much Fun (which in her case essentially means food and cigarettes) she has every day before dying. And she has nearly explicitly admitted to that. (And no, I’m not just talking about the fact that she eats and smokes too much.)
I’m very skeptical of reasoning like “it was like that in ancestral environment so it must be good”. There are at least three reasons that makes me uncomfortable with the reasoning :
Even if we consider evolution to be a perfect optimizer (which it is not), there is a huge difference between “our digestion system is optimized to make the best possible use of food X” and “food X is best possible food for our digestion system”. If you made an algorithm A optimized to transmit data on a noisy channel N, it doesn’t mean the algorithm wouldn’t run better on a less noisy channel C. There may be an algorithm B that work better on the clear channel C than A, but still, A can work better on C than on N.
Evolution doesn’t optimize for the same purpose we do. Evolution doesn’t optimize for us to live long, it has a very low pressure to make us live past ~60, for example.
We have completely different lifestyles and activities than we did during paleolithic. And the optimal diet very likely depends of lifestyle and activities.
That said, what would convince me to do a diet is not a plausible-sounding reasoning, but some evidence of short-term and long-term effects on a sane sample size, with a control group. Something which seems very rare in the diet field, saddly.
Your grounds for skepticism match the heuristic that Anders Sandberg and Nick Bostrom propose in The wisdom of nature quite closely. They propose this heuristic to evaluate interventions to enhance humans, but it’s clear that it has much broader applicability. Here’s the relevant excerpt:
You should start the excerpt earlier to explain what is meant by EOC:
Gwern discusses these on his drug heuristics page.
Evolution doesn’t stop. We have continued to evolve, adapting to new environments, including foods.
But it’s really slow, some new traits are lactas in adult age, gluten tolerance, but rerouting your entire metabolism is something altogether. Besides optimising from evolutions point of view (e.i. maximise reproduction) is not the same as optimising from most peoples point of view (e.g. living longer, being healthy past middle age).
Most living people don’t optimise for that either. If they did, more would practice calorie restriction.
I’ve yet to see any evidence on the effects of calorie restriction on humans. Mice are quite different from us, and all evidence on calorie restriction I’ve seen was done on mice.
Also, there is no just how long you live, but also life quality. We know the brain is a massive consumer of calories. We know that when people are even in light hypoglycemia, their reflexes and cognitive abilities go down. I never saw any study on the effects of calorie restriction to attention, reflexes and cognitive abilities.
Some human research is listed here.
There are plenty of studies on that—e.g. start here.
Evidence on humans can be found through here, and extensive discussion on evidence in macaques can be found here (although I recommend reading the whole discussion and/or the study; the root comments are less informed than the leaf comments).
I believe there have been encouraging experimental results in other mammals, including primates, as well as human trials with surrogate endpoints. I also recall seeing a least one ongoing prospective cohort study with promising interim results. Will google and append links when I get a moment.
I would expect mild ketosis to compensate for hypoglycemia, but cognitive effects are of concern to me as well. Anecdotally, while practicing intermittent fasting regularly I did not appear to suffer any cognitive impairment.
I do feel (but yes, that’s error-prone) that I’ve lower concentration/thinking ability when I’m late for a meal.
Also, my parents (both retired teachers, one at uni the other in secondary school) both noticed that pupils/students were less focused and more error-prone in the hour just before lunch, and AFAIK (but I’ve no link right now to point at) this was backed by more formal studies than just “personal experience”.
There is also a certified increase of rate of car accidents in Muslim countries during the Ramadan month, due to lower attention/reflex speed when people are doing Ramadan, but AFAIK it’s unsure how much is because of hypoglycemia and how much is because of dehydration.
Edit : for my own personal experience, it may also be because I’m on the skinny part of the spectrum, I weight ~55kg for 170cm, so I get hypoglycemia quite fast if I don’t feed enough or regularly, it may very well be different for people who have more reserves than I do.
Being late for a meal is very different than restricting calories. If you eat a meal at the same time every day, your body gets in the habit of wanting to digest food at that point in the day. More blood re-routed to digestive system, less blood to the brain --> lower concentration/thinking ability before meal. Note I am partially pulling this out of my ass.
I feel better when coming back from lunch, so it’s not the “re-routing blood to the digestive system”. But it could be something with sugar level management, yes, my body expecting to be fed at 1pm, so not taking the expense to start using stocks to provide me with sugar when we are near that time, instead waiting for the coming meal, or something like that.
Anyway, I more wanted to say that diet/calories issues aren’t simple, and that “rodents live 20% longer when on calorie restriction in a lab” is just weak evidence that it would be good for us to do so. There are many aspects to consider (differences between men and rodents, effects on intellectual abilities or overall well-being, immune system strength, capacity to recover in case of disease/wound, effects on different ages, sex or corpulence, …) and studies that evaluate all of that are lacking.
Maybe calorie restriction is worth it, but there is just not enough evidence to tell. Saying “Most living people don’t optimise for that either. If they did, more would practice calorie restriction.” seems to me broad overconfidence.
Interestingly, the calorie restriction effect may just be because the mice used were overweight. article
Ironically, given the Western diet, even if that is ‘all’ CR is, it may still be a good idea and life-extending.
In sensible CR experiments (which date back to the 1950s) the control mice are calorie restricted too, precisely in order to rule this possibility out.
Discussed here; timtyler’s aware of such results and believes the evidence still points towards CR (which is also my opinion).
What about the Okinawans?
What about them? They eat more and differently these days, and accordingly, Okinawa’s life expectancy has fallen.
I was thinking about the pre-WWII Okinawans. Anyway, isn’t what you mention further evidence that CR works, even below the not-morbidly-obese line?
It could be, yes. One question I have here is what is ‘morbidly obese’? Is it like IQ, where it’s essentially a relative ranking (the top fifth is the fattest and defined as morbidly obese), or do we have a clear bright line from biology where a certain weight is the crossing point between good and bad? If it is the former, then for all we know, Okinawans who were eating their fill were still above the bright line even though they look thin and fit from a contemporary American viewpoint.
Yes. My grandmother seems to not give a damn about how much longer she’s going to live, only about how much Fun (which in her case essentially means food and cigarettes) she has every day before dying. And she has nearly explicitly admitted to that. (And no, I’m not just talking about the fact that she eats and smokes too much.)