When you eat, your gut releases a hormone called glucagon-like peptide-1 — GLP-1. It travels to your brain, your stomach and your pancreas, signalling that food has arrived. The stomach slows its emptying. Insulin rises. Appetite falls. For most of human history, this was a short-lived signal, gone within minutes.
What GLP-1 medications do is mimic and prolong that signal. Semaglutide, the active ingredient in Ozempic and Wegovy, is a molecule engineered to bind to the same receptors as natural GLP-1 — but to resist the enzymes that would normally break it down within minutes. The result is a hormone signal that lasts not minutes but days.
The effect on appetite is the one people notice first. Patients consistently describe a reduction in what researchers call “food noise” — the background hum of hunger and food preoccupation that, for many people living with obesity, has been a constant presence for years. The stomach empties more slowly, which extends the feeling of fullness after meals. Together, these effects make eating less feel natural rather than effortful.
But the mechanism extends well beyond appetite. GLP-1 receptors are found throughout the body — in the heart, the kidneys, the brain and the immune system. The SELECT trial, published in 2023, demonstrated a 20% reduction in major cardiovascular events in people with obesity who took semaglutide but did not have diabetes. Researchers are now investigating effects on kidney disease, liver disease, cognitive function and addiction.
The honest answer to “how does it work?” is: more ways than we currently understand. What we do know is that GLP-1 receptors were not designed to be activated at pharmaceutical doses. We are, in an important sense, running an experiment. The early results are extraordinary. The long-term picture is still being written.
Sources
- Müller TD et al. Glucagon-like peptide 1 (GLP-1). Mol Metab. 2019;30:72-130. doi:10.1016/j.molmet.2019.09.010
- Lincoff AM et al. Semaglutide and Cardiovascular Outcomes in Obesity without Diabetes (SELECT). N Engl J Med. 2023;389:2221-2232
- Drucker DJ. The biology of incretin hormones. Cell Metab. 2006;3(3):153-165