[SAI_Peregrinus]

CICO is true, but it misses that some sources of calories are more satiating than others. So the desire to consume more calories will be higher with the less-satiating foods. The thermodynamics work fine, but to create a long-term behavioral change you also have to prevent the discomfort of hunger.

For some people hunger isn't particularly uncomfortable (e.g. I often barely notice it and have to set calendar reminders to remember to eat), for other people it's actively painful and nearly impossible to ignore.

CICO is true, but it's only solving the easy half of the problem.

[AstralStorm]

Satiation is only relevant in the short to medium term, while you're adjusting to the diet. It's been tested with super low volume foods way back. And unfortunate starvation experiments, people literally stop feeling hunger just go weak.

Ultimately the system is feedback based.