[Vecr]

> the optimum is a bit thicker than our guidance suggests

That's probably confounded. Anything over a BMI of 23 better be an increasing proportion of muscle, and even then there's a point that the stress on the heart isn't worth it.

Almost every physical and mental heath condition does bad things to nutrition and internal energy stores, even if only at a diet level.

It's hard to see since so many people are overweight or obese to start with, but the overall correlation goes that way enough to cause confounding.