Your body already makes a hormone that tells your brain you're full. GLP-1 medications work by mimicking it — turning up a signal that was always there but, for many people, never quite loud enough to override the drive to keep eating.
GLP-1 (glucagon-like peptide-1) is released by your gut after you eat. It signals your brain that a meal is under way — slowing digestion, dialling back appetite, and helping regulate blood sugar. The catch: your body breaks natural GLP-1 down within minutes. The medications are engineered versions that resist that breakdown, so the signal stays active for days — which is why one injection covers a week.
Some medications, including tirzepatide (Mounjaro), act on two receptors rather than one: GLP-1 plus GIP, another gut hormone involved in appetite and fat metabolism. The combination appears to amplify the effect on fullness and weight loss. Your clinician recommends the right medication for your situation.
Worth being direct about: the medication makes a calorie deficit easier to sustain — it doesn't create results on its own. Protein and resistance training matter even more while you're losing, so the weight that goes is fat rather than muscle. Keeping muscle while you lose fat covers exactly how.
How your dose steps up, why you started low, what to do about early side effects — it's all covered in Your first 90 days on medical weight loss, or just message the care team. We'd rather explain it twice than have you guess once.