How do GLP-1s cause weight loss?

Three mechanisms run simultaneously: 1. Brain-level appetite suppression. GLP-1 receptors in the hypothalamus and brainstem turn down hunger signaling. People describe smaller appetite, earlier fullness, and — most strikingly — the disappearance of constant background thoughts about food (“food noise”). 2. Slowed stomach emptying. Food physically stays in your stomach longer, so a modest meal produces hours of satisfaction instead of minutes. (This same mechanism causes the nausea and reflux side effects.) 3. Reduced reward-driven eating. GLP-1 receptors also live in the brain’s reward circuitry. Many users report cravings, stress-eating, and even alcohol interest dropping — an area of active research. In controlled feeding studies, people on semaglutide spontaneously ate roughly 24–35% fewer calories at a buffet meal without being told to restrict. That sustained, comfortable deficit — not fat-burning — produces the weight loss. The corollary matters: because the drug works by suppressing intake, the quality of what you do eat (especially protein) and resistance exercise determine how much of the loss is fat versus muscle.