I think one of those cases of ecological/population fallacy "interpretation of statistical data that occurs when inferences about the nature of individuals are

I think one of those cases of ecological/population fallacy "interpretation of statistical data that occurs when inferences about the nature of individuals are deduced from inferences about the group". There is enough genetic diversity that some individuals can out work their caloric intake (bmr + tdee). You see it all the time in enviroments where high level athletes train. You'll have groups that still need to manage intake to keep weight off, and you'll have groups that can eat everything in sight and still stay lean, or even be forced to go into surplus to maintain. IMO (bro science) it seems to largely boil down to whatever factors that affect rate at which individuals shit. Most of the naturally skinny people I know, either eat not much, or eat normal amount but shit often. When the normal range of people pooping is 3x per day to 3x per range, it matters how inefficient your body absorbs/wastes the calories you put in. Some people's bowels are natrually bulimic, purges everything all the time and keeps weight down. Maybe it's not useful to apply to genpop (abs built in kitchen etc), but I don't feel it's a paradox.