If you want to know why people get obese, it seems to me that one avenue would be to also look at people who neither diet, nor live in scarcity, nor get obese. What is happening differently in their bodies? Has anyone studied this?
people have tried. Almost everything you find thin population X does, you have another thin population that does exactly the opposite. IIRC “Speaking English makes you fat” was a joke but also more empirically supported than the leading candiates.
I am not aware of a low BMI population in which consumption of processed western food is just as common as it is in high-obesity regions. This seems to be an important counterexample.
Highly processed food became dominant well before the great obesity-ing started, right?
Do we have evidence of that? As far as I can tell, the SMTM authors merely argue that some specific brands of processed food were available starting from the late 19th century, not that “highly processed food became dominant before the great obesity-ing started,” which is a much stronger claim.
Also, as I argued in this post, the obesity epidemic arguably started way before the SMTM authors often seem to imply it did. Quoting myself:
And it’s not as if Americans were that thin in the early 1970s! 47% of adults were overweight and 14.5% obese (a). In contrast, obesity rates are under 3% in traditional societies that engage in foraging or subsistence farming. Moreover, there is substantial (a) evidence (a) that Americans gained a lot of weight before 1970. It’s hard to know the overweight and obesity rates of the general population back in the 19th century, because there was no NHANES back then, but we do know that men at elite colleges (a) (source), Citadel cadets (a) (source) and veterans all started getting substantially fatter in the early 20th century.
I feel the need to stress this, because the SMTM authors claim (a) that there was an abrupt shift in obesity rates in the late 20th century, a claim that is probably based to some extent on an artifact of the definition of BMI (a), and so some people reading this might have the impression that 1970s Americans were really thin or something, when they really weren’t.
Here are a few charts from the sources I linked to. From this VoxEU article:
Man I’d love to get this data with BF% rather than BMI (I realize this is not your fault and BMI is usually all that’s available, this is a complaint about the field). BF% increase obviously increases BMI, but so does muscle and height-while-keeping-BF%-the-same (because BMI doesn’t scale quite right with height).
Overall I find the second and third graphs especially convincing but would need to think more before updating, thanks for highlighting those.
The answer might be genetics, so while that would be potentially interesting from a gene therapy point of view, if we find a food contaminant or environmental pollutant is causing the obesity epidemic, that might be much easier to fix—by banning it. After all, there might be many genes of individually small effect involved in resistance to this hypothetical contaminant or pollutant, and those genes might have all sorts of side-effects.
But you are right that by studying these people, and comparing them to obese people, we might in principle discover some (altered) biochemical pathway that is enlightening to know about.
If you want to know why people get obese, it seems to me that one avenue would be to also look at people who neither diet, nor live in scarcity, nor get obese. What is happening differently in their bodies? Has anyone studied this?
people have tried. Almost everything you find thin population X does, you have another thin population that does exactly the opposite. IIRC “Speaking English makes you fat” was a joke but also more empirically supported than the leading candiates.
EDIT: found it
I am not aware of a low BMI population in which consumption of processed western food is just as common as it is in high-obesity regions. This seems to be an important counterexample.
Does the timing work out with that? Highly processed food became dominant well before the great obesity-ing started, right?
Do we have evidence of that? As far as I can tell, the SMTM authors merely argue that some specific brands of processed food were available starting from the late 19th century, not that “highly processed food became dominant before the great obesity-ing started,” which is a much stronger claim.
Also, as I argued in this post, the obesity epidemic arguably started way before the SMTM authors often seem to imply it did. Quoting myself:
Here are a few charts from the sources I linked to. From this VoxEU article:
A chart by Random Critical Analysis, using data from this book:
A chart made with fancy statistical modeling, from this paper (note that the x-axis is each cohort’s birth year):
This is also relevant (from Random Critical Analysis as well):
We can see that BMI increases superlinearly with body fat %, so if body fat % is linearly growing in a population, BMIs will accelerate.
Man I’d love to get this data with BF% rather than BMI (I realize this is not your fault and BMI is usually all that’s available, this is a complaint about the field). BF% increase obviously increases BMI, but so does muscle and height-while-keeping-BF%-the-same (because BMI doesn’t scale quite right with height).
Overall I find the second and third graphs especially convincing but would need to think more before updating, thanks for highlighting those.
The answer might be genetics, so while that would be potentially interesting from a gene therapy point of view, if we find a food contaminant or environmental pollutant is causing the obesity epidemic, that might be much easier to fix—by banning it. After all, there might be many genes of individually small effect involved in resistance to this hypothetical contaminant or pollutant, and those genes might have all sorts of side-effects.
But you are right that by studying these people, and comparing them to obese people, we might in principle discover some (altered) biochemical pathway that is enlightening to know about.