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Why BMI is flawed — and how to redefine obesity
(www.nature.com)
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this post was submitted on 11 Oct 2023
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It doesn't really work at that either.
You can't use it tell if soccer players are fatter on average than rugby players or if Japanese people are fatter than Samoans. Or even if men are fatter on average than women.
But these are population questions.
I think that's just more examples of it being misused. BMI may be useful to compare populations in certain instances. It has value in being easily calculated based off data that is often easy to obtain. But, there are many situations where it would be inappropriate to use BMI for statistical comparison. That doesn't mean it's entirely useless.
I mean BMI is also useful for comparing individuals in certain instances. That's why doctor's use it.
It's a crappy measure, but it's good enough for a range of use. You just have to be thoughtful enough to say, yeah it's not going to work for this person.
I'm not anti BMI, I'm just opposed to people repeating statements like "BMI is useful to compare populations" which don't really mean anything.
You can use it after controlling for the variables that would otherwise skew it.
Comparing different sports with different muscle requirements, or different genders with different muscle development, would be a wrong use.
Comparing averages of samples of Japanese vs. Samoans, with the same ratio of males vs females, sporty vs non-sporty, and a similar age distribution, would be a viable comparison.
INB4 genetic differences between Japanese vs Samoans:
"Over the period of 1978-2013, in a population of approximately 200,000 Polynesian people, the prevalence of obesity increased from 27.7% to 53.1% in men (2.3% per five years) and 44.4% to 76.7% in women (4.5% per five years)"
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9012561/
You should have kept reading about BMI.
This isn't about speculative genertc factors it's about medical boards arguing that the thresholds need to be set differently for these populations.
https://cks.nice.org.uk/topics/obesity/diagnosis/identification-classification/
Similarly, new Zealand used to have higher thresholds for obesity for Maori and Polynesian (which includes Samoa), but because a range of issues including diabetes is such a problem for these populations they brought it back down. It still doesn't work reliably as a risk factor for a range of stuff.
https://medicalxpress.com/news/2020-06-bmi-inconsistent-obesity-maori-pacific.html