[Jenda_]

> Posts like Jenda's are depressingly unimaginative. I wish HNers, and people in general, would learn some biology, and use some critical thinking to imagine that when something doesn't fit their very basic mental model, that's probably because there's exponentially more to know/learn(!).

That's why I was not disputing the premise (like previous commenters did), but asking for possible explanations!

[layla5alive]

I apologize, you're right - you were sincerely questioning "where does the energy go?" - which is laudible. I mistakenly read your post as insincere and lumped you in with the others who were being dismissive. I should have directed my criticism at grandparent posters.

There's definitely a heat-loss phenomenon - look for skinny kids in shorts in 40 degree weather - but it's also the case that a variable amount of input calories can be discarded without full digestion by the body - energy not even extracted for use. The religiously calories in : calories out folks assume a linear digestion efficiency relationship between total calories consumed and that this holds unifomally across the population. Given the complexity of biology, they should be unsurprised that there will be myriad outliers

[naijaboiler]

this. Yes the physics of weight is ridiculously straight forward. Its first law of thermo (calories in = calories out). The biology is incredibly complex and that's before we get to the pyschological, to the point of making CICO too overly simplistic to describe actual practical reality. The body is not some perfect energy converting mechanical machine.

People also forget "metabolism doesn't change with age" narrative is a based on a paper that used population-wide statistical model. That approach measures "average treatment effect" and is directionally useful in general but incredibly unhelpful in addressing individual differences and nuances. Something is true on average does not mean it is true "for every" or even "for any"