CICO is more of an upper bound, but people like to incorrectly use it as a lower bound. Meaning that it's true that you can't burn more calories than you eat, but you can certainly eat many more calories than you store as fat.
(Hell, CICO isn't even valid for something as "simple" as an electric vehicle. My EV's end-to-end efficiency is quite a bit different depending on whether I'm charging from 120V or 240V, the outside temperature at charging time, the outside temperature at driving time, and a handful other factors like state-of-charge. The human body is even more complicated.)
(Hell, CICO isn't even valid for something as "simple" as an electric vehicle. My EV's end-to-end efficiency is quite a bit different depending on whether I'm charging from 120V or 240V, the outside temperature at charging time, the outside temperature at driving time, and a handful other factors like state-of-charge. The human body is even more complicated.)