How the brain adds it up
All of these signals meet in the hypothalamus. The classic dual-center model pits a lateral "start" center against a ventromedial "stop" center. The running balance of hunger and fullness signals decides whether you eat. Newer research shows the real wiring is more of a network, including the arcuate nucleus, than two neat switches. But the start-versus-stop logic still holds. Over the long run, weight tends to settle at a level your habits and surroundings support. Researchers call this a settling point. It is a softer version of the older set point idea. The weights in this model are made up to show the logic, not measured values.