[bumby]

I agree that the CICO is a model that works, but it is at least somewhat complicated by the fact that CO is a function of CI. I.e., what you eat takes different amounts of energy to metabolize so it also contributes to what you burn. If I eat 1800 kcal of protein I may have higher CO than if I ate 1800 kcal of simple carbohydrates.

There's already a lot of uncertainty when most people measure their calories (very few people actually weigh their food) and this just adds another layer of uncertainty. I have a feeling those all combine to make it inaccurate enough in practice for some people to claim the CICO model doesn't work.