Do GLP-1s burn fat or just reduce appetite?

The “fat-burner” framing is marketing residue from the supplement world; GLP-1 physiology is different and worth understanding because it changes how you use the drug. What the drugs actually do: suppress intake. In feeding studies, semaglutide users spontaneously ate ≈24–35% less at test meals. Fat leaves your body the only way it ever does — by being metabolized to cover the gap between what you burn and what you eat. The drug builds the gap; ordinary metabolism does the burning. What they don’t do: raise your metabolic rate. There’s no thermogenic effect at current-drug doses. In fact, as with all weight loss, your total burn declines as you shrink (smaller bodies cost less to run, plus some adaptive slowdown). This is exactly why plateaus are inevitable and why “the drug stopped working” is usually a misreading. The practical consequences of appetite-only mechanics: 1. What you eat within the smaller budget decides body composition. The drug doesn’t care whether the deficit comes out of fat or muscle — protein and lifting decide that. 2. Liquid calories are the bypass. Appetite suppression poorly polices drinks; they’re the classic stall cause. 3. Stopping removes the gap, not the biology. Appetite returns; the burn stays low for a while — the regain mechanism in one sentence. The pipeline footnote: glucagon-receptor agonism (the third arm of retatrutide) genuinely increases energy expenditure and liver-fat burning — the first real “burn more” mechanism in the class, and part of why its trial numbers broke records.