[nerb]

You reference the laws of thermodynamics, but I'm not sure which laws you're applying to the human body? Is it the first which requires the measured system to be closed which a human body is not? Is it the second about entropy always increasing? Or is it the third defining perfect entropy at 0 Kelvin?

Bringing up thermodynamics as a generalization for biological systems is pseudo-intellectual. We aren't all equal machines that take in a fuel stock and output work. How do you account for differences in peoples' resting metabolic rates? How do you account for the difference in available energy in the foods you chose to eat, and in the differences in peoples' biological processes that extract that energy? Stress is a common hormonal modifier that impacts how the body stores fat; no where near a "rare" condition that many people experience nowadays, and yeah caused by things like sleep apnea. You betray your own argument anyway by adding an the "hormonal condition" exception (I don't see any exceptions referenced in the laws of thermodynamics, lol).

Biology has more dimensions than you are choosing to look at, and using thermodynamics as a "gotcha" when it comes to others' bodies reveals your lack of understanding and intuition.

[foobarian]

Yes the first one. The energy contained in ingested food is far and away the dominant metabolic input.

There is no need to get into the weeds of various details of how that breaks down; the main problem is that calories are way too cheap in the modern day and age, and people's habits and instincts developed in far different eras lead to easily ingesting more than is expended. Yes the OP is not wrong, but it's not a very useful argument unless we're going to roll back the modern civilization.