[mrguyorama]

It's funny too, because I have perfectly logged data showing that the weeks I eat fewer than about 1800 calories reliably, (because I have an incredibly sedentary lifestyle) reliably and predictably lower my weight.

I've literally got a science experiment in my own body that shows reducing calories in, without reducing the actual design of my meals, reduces my body mass.

I'm willing to accept that there are some minor irregularities and difficulties that make "Calories in == Calories out" not 100% accurate, but I'm betting the effect size is closer to +-10%, and therefore easily discarded for approximations, even though they are scientifically significant and could create a more accurate model.

[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.