[cimmanom]

The point is that the reason that there's so much diet advice out there beyond calories in < calories out is that accomplishing calories in < calories out on an ongoing basis is HARD.

The advice (aside from the scams and a little bit of idiocy) is on how to achieve that deficit in a way that minimizes the willpower required - because humans suck at willpower and one's biology is constantly trying to undermine that willpower in order to achieve the "store more reserves" imperative.