Hell I can eat a whole 2000 calorie pizza and be hungry 3hrs later. One explanation is that the body shaves off 20% FIRST and sends that right to fat (triggered by insulin in the white dough). You don't get a say in the matter. So you have 80% of the calories left to use, but almost no nutrients in any of them. Anyhow after the sugar crash you feel like dog poop and want to eat more for more cheap energy...also you want to eat more because you never got your nutrients and your body is confused how it got full yet is still starving, and so on and so forth.
Thus "calories in / calories out" isn't very useful in explaining the "pizza/cake endless chow-down" scenario.
It isn't very useful in explaining a lot of scenarios.