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by afiori 1388 days ago
Obesity implies high BMI, but not vice versa.

Fat is not the only way to be heavy, body builders have very high BMI value yet have very different risk profiles.

1 comments

The poster above states outright that you don't have to be a bodybuilding to have high BMI though. You just have to be tall and lift occasionally? Thus my confusion.

Also, I'm still confused. My previous understanding was that bodybuilders are classified as obese without having excess body fat because they fit into that ratio because the ratio doesn't account for exceptions. Not that obesity actually incorporates more than just a ratio.

As other commenters noted, BMI is just a low fruit metric to open the door for more investigations (or not). And when you see the person I bet you'll know immediately whether it applies or not. The word "obesity" existed well before BMI.
BMI uses an exponent of 2, for physical reasons it needs to be around that value, but the "correct" value might be different; it appears that GP believes it should be higher.

The point about body builders is that BMI as a metric assumes a fixed muscular profile, so doing (an healthy amount of) muscle training can wildly affect your BMI independently of your fatness.

If is still likely a good measure at a population level as very few people that have BMI > 30 are also fit. But you need to contextualize it to your own case.

To be more precise, my problem with this study is when you select for people with BMI>30 and filter for those who do not have obesity related health issues, you’re going to have a lot more of the pathological case, like body builders, tall folks who are overweight but not obese, etc.