CICO or not has got to be best long-term argument going here.
I’d say that obviously, it works - it has to work, it’s just physical reality. We’re not talking about ‘magic’ - boil it down enough and to a vast extent our weight is dependent on atoms of carbon, hydrogen, oxygen and nitrogen coming and going.
This is not to say that “CICO” alone and in it’s most primitive/misunderstood form will necessarily be a good way for a given person to lose weight. It’s certainly not for me, nor for hundreds of millions or even billions of people, worldwide. This is because of the hormonal effects - well addressed by several people, above - that can alter the equation.
CICO is just the messenger - saying what’s happening. If we change the equation by having such hormonal effects - a slowing metabolism, being in ‘fat-storage’ mode rather than in ‘fat-burning’ mode due to high insulin, etc., then we’re not disproving CICO, we’re just denying the very premise of it.
The odds are extremely high, indeed. Jenny Craig’s own figures showed only a 0.5% success rate for their customers losing weight and keeping it off for two years afterwards.
Yeah, the individual has to be open to it, or at least open to something other than the poorly-working dietary advice that is ingrained in them. People do “get religion” about diets, and sometimes at the best it’s like pushing on a string, trying to convert them (even though keto may be the best avenue for them).
There are many individuals and corporations with a monetary interest in keeping people away from ketogenic diets - there’s a constant barrage of silly, untruthful, half-truthful, deliberately misleading articles, blog posts, even studies, etc. - sometimes it’s hard not to rant and rave and be zealous…