Your body doesn't decide to eat on a whim. A stream of chemical and mechanical signals — from an empty stomach, the bloodstream, the gut, fat cells, and the brain itself — pushes appetite up or reins it in. Tap each signal to see where it comes from and whether it tells the brain to start or stop eating.
Where hunger comes from
◀ START eatingSTOP eating ▶
The needle shows which way this signal pushes appetite.
The hunger systemtap a signal to begin
How the brain adds it up
All of these signals converge on the hypothalamus. The classic dual-center model sets a lateral "start" center against a ventromedial "stop" center, and the running balance of hunger versus satiety signals decides whether you eat. Over the long run the body defends a fairly stable weight — its set-point — nudging appetite up or down to keep energy stores roughly constant. Newer research shows the real circuitry is more of a distributed network than two tidy switches, but the start-versus-stop logic still holds.