GLP-1 Receptor Agonists

GLP-1 is a hormone naturally released from the gut after eating that increases insulin secretion in a glucose-dependent way (reducing hypoglycemia risk compared to some older diabetes drugs), suppresses glucagon, slows gastric emptying, and acts on appetite centers in the brain to reduce food intake. Drugs in this class, including semaglutide (Ozempic, Wegovy) and the dual GLP-1/GIP agonist tirzepatide (Mounjaro, Zepbound), are modified to resist rapid enzymatic breakdown, allowing once-weekly dosing.

Weight-loss efficacy is well established in large randomized trials: the STEP trial program for semaglutide and the SURMOUNT program for tirzepatide both showed average weight reductions in the range of 15–20% of body weight over roughly 68–72 weeks in participants with obesity, substantially more than prior weight-loss drug classes. Beyond weight, the SELECT trial (2023, New England Journal of Medicine) found that semaglutide reduced major adverse cardiovascular events in people with pre-existing cardiovascular disease and overweight/obesity but without diabetes — evidence for a cardiovascular benefit that appears to extend beyond weight loss alone.

This drug class is a genuine advance with strong randomized trial evidence for its approved indications (type 2 diabetes, chronic weight management, and now cardiovascular risk reduction in the specific SELECT population), which distinguishes it from most compounds in this glossary. It is not framed or approved as a general longevity or anti-aging drug, common side effects (nausea, gastrointestinal symptoms) affect a substantial minority of users, a rare but serious risk of gastroparesis and other GI complications has been reported, and long-term outcome data beyond a few years of use is still accumulating.