Semaglutide

Semaglutide is a synthetic, longer-lasting copy of GLP-1, a hormone your gut releases after eating. It's built to resist DPP-4, the enzyme that normally breaks GLP-1 down within minutes, so it stays active for about a week — which is why it's dosed once weekly. It works by switching on the GLP-1 receptor, found on cells in the pancreas, the gut, and several appetite-controlling regions of the brain.

Its effects come from hitting all of those sites at once. In the pancreas it tells beta cells to release insulin, but only when blood sugar is high, and it dials down glucagon (which raises blood sugar) — so it lowers glucose with little risk of dropping it too far. In the brain it acts on hunger circuits in the hypothalamus and brainstem to increase fullness and reduce intake, and in the stomach it slows emptying so meals feel satisfying longer.

That combination is what produces both the blood-sugar control behind its diabetes approval and the appetite reduction behind its weight-management approval. It's among the most heavily trialed peptides in medicine (SUSTAIN, STEP, SELECT). The trade-offs are mostly gastrointestinal — nausea, especially during dose escalation — and the class carries a precautionary thyroid C-cell warning based on rodent data.