The GLP-1 Receptor, Explained

GLP-1 is an incretin hormone released by the gut (L-cells) in response to food. It amplifies glucose-dependent insulin release from pancreatic beta cells, suppresses glucagon, slows stomach emptying so you feel full longer, and acts on brain satiety centers. Semaglutide resists the rapid DPP-4 degradation that native GLP-1 suffers, extending its action to a full week.

This extended activity is the key to both its efficacy and its side-effect profile, which is dominated by delayed-gastric-emptying effects (nausea, early fullness).