None of those metrics would catch if a contaminant makes some people very fat while making others thin ( SMTM thinks paradoxical effects are a big deal, so this is a major gap for testing their model).
So, contra what the SMTM authors argue, whatever is causing the obesity epidemic does not seem to be spreading out the BMI distribution so much that being extremely thin is more common now.
I apologize for commenting so much on this post. But here is more evidence that, contra SMTM, being underweight is a lot less common now, not more common:
The same trend can be seen in the rest of the world (the purple category is the percentage of the population that is underweight):
I don’t know why they say that being underweight is more common now, given that that is literally the opposite of the truth, and given that it is quite easy to figure that out by Googling.
It is true that the variance in BMI has increased, but that is entirely due to higher BMIs being more common. Here are (sampling weight-weighed) KDEs of the distributions of BMI in the early 70s (orange) versus 2017-2020 (blue) in the United States, using data from NHANES:
FWIW, it does not seem to be the case that, at a population level, very low BMIs are more common now than they were before 1980. The opposite is true: when you compare data from the first NHANES to the last one, you see that the BMI distribution is entirely shifted to the right, with the thinnest people in NHANES nowadays being substantially heavier than the thinnest people back then.
So, contra what the SMTM authors argue, whatever is causing the obesity epidemic does not seem to be spreading out the BMI distribution so much that being extremely thin is more common now.
I apologize for commenting so much on this post. But here is more evidence that, contra SMTM, being underweight is a lot less common now, not more common:
Underweight rates have decreased almost monotonically in the US over the past several decades.
The same trend can be seen in the rest of the world (the purple category is the percentage of the population that is underweight):
I don’t know why they say that being underweight is more common now, given that that is literally the opposite of the truth, and given that it is quite easy to figure that out by Googling.
It is true that the variance in BMI has increased, but that is entirely due to higher BMIs being more common. Here are (sampling weight-weighed) KDEs of the distributions of BMI in the early 70s (orange) versus 2017-2020 (blue) in the United States, using data from NHANES:
The code I used to create this plot is here.