> If calories in, calories out was useful advice rather than a banal statement of physics

it's also wrong, or at least imprecise. fat and bone and muscle all weigh different amounts, at the same volume.

the only way i've been able to explain the science to laypersons is thus:

if you and a friend both weigh 200lbs, but you once weighed 250lbs and your friend has never weighed more than 200lbs; all else equal: you must ingest less calories than your friend to maintain 200lb body weight.

your body will try to "outlast the famine" if you had to lose a lot of weight (or lost a lot of weight for any reason).

That absolutely does not comport with "calories in, calories out". It's also why the people who were never fat have no problem "just eating a donut."

no, i won't cite, this has been published many times in the last decade, 13 years.

Eh, it totally does comport with calories in, calories out. We just don't hook people up to metabolic carts in day-to-day life, but that's really the only way to measure the calories out part.

The physics of CICO are undeniable. Humans don't photosynthesize. The biology of CICO is useless.

- former fat guy. I'm deeply, personally aware of how useless CICO is as dietary advice.