Tirzepatide is a GIP and GLP-1 receptor agonist, so it works (mechanism of action) by activating both GIP (glucose-dependent insulinotropic polypeptide) and GLP-1 (glucagon-like peptide-1) hormone receptors. GLP-1 helps control appetite and calorie intake, and GIP is thought to contribute to regulating food intake as well. It works for weight loss by decreasing appetite and slowing the movement of food from the stomach into the small intestine, which may make you feel full more quickly and for a longer period of time.