Weight loss is not simply a test of willpower. The human brain evolved to protect body fat during times of scarcity, and it can treat a previously higher weight as the new normal, triggering stronger hunger, cravings, and lower energy use after weight loss. This biological “memory” helps explain why many people regain weight after dieting and why medications such as Wegovy and Mounjaro can help by reducing appetite signals, although their effects may fade when treatment ends.