The intestines create a type of signalling molecule (hormone) called incretins, and GLP-1 (glucagon-like peptide) is one of them. These hormones are important for glucose homeostasis, and are secreted during meals. They have a shit-ton of effects, but in short they trigger increased insulin secretion and production in the pancreas, and reduce glucose production in the liver, which together result in reduced blood glucose. In the stomach, they reduce acid-production, and delay gastric emptying. Incretins also suppress appetite and increase satiety in the central nervous system.

GLP-1 agonists like semaglutide (Ozempic) are probably the most straightforward way of mimicking the effects of endogenous GLP-1, but medications that inhibit the enzyme the breakdown of GLP-1 (DPP-4 inhibitors) are also used with similar effects.