How it seems to be typically used, literal CICO as an observation is the motte, and the corresponding bailey is something like: "yes, it is simple to lose weight, you just need to stop eating all those cakes and start exercising, but this is the truth you don't want to hear so you keep making excuses instead".

How do you feel about the following theory: "atoms in, atoms out"? I mean, this one should be scientifically even less controversial. So why do you prefer the version with calories over the version with atoms? From the perspective of "I am just saying it, because it is factually true, there is no judgment or whatever involved", both theories are equal. What specifically is the advantage of the version with calories?

(My guess is that the obvious problem with the "atoms in, atoms out" theory is that the only actionable advice it hints towards is to poop more, or perhaps exhale more CO2... but the obvious problem with such advice is that the fat people do not have conscious control over extracting fat from their fat cells and converting it to waste. Otherwise, many would willingly convert and poop it out in one afternoon and have their problem solved. Well, guess what, the "calories in, calories out" has exactly the same problem, only in less obvious form: if your metabolism decides that it is not going to extract fat from your fat cells and convert it to useful energy which could be burned in muscles, there is little you can consciously do about it; you will spend the energy outside of your fat cells, then you are out of useful energy, end of story, some guy on internet unhelpfully reminding you that you didn't spend enough calories.)