What is GLP-1, and why does a gut hormone matter for weight?
A hormone released when you eat helps run insulin, the stomach and appetite at once, and it lasts only two minutes.
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GLP-1, short for -like peptide-1, is a hormone your gut releases when you eat. It does several jobs at once: it helps the pancreas release insulin when blood sugar is high, it slows the rate at which the stomach empties, and it sends a fullness signal to the brain. That mix of effects on blood sugar and appetite is why a hormone from the gut ended up at the centre of weight-loss medicine.
The clue came from an experiment. Swallowed glucose triggers a bigger insulin response than glucose given into a vein that reaches the same blood level. That gap is called the incretin effect, and it means the gut must send a message after a meal. In 1932 the Belgian physiologist Jean La Barre used the word "incretin" for gut hormones that stimulate insulin release, and he suggested they could treat diabetes. GLP-1 is an incretin, and so is a second hormone called GIP.
Step 1: You eat
Food reaches the intestine
Step 2: Gut cells release GLP-1
Intestinal L-cells make the hormone
Step 3: Pancreas
More insulin when sugar is high, less
Step 4: Stomach
slows
Step 5: Brain
Signals fullness
Step 6: clears it
of about 2 minutes
Finding GLP-1 was slow, human work. In the 1980s Svetlana Mojsov was identifying it at Massachusetts General Hospital, where she headed a peptide synthesis facility. She, Daniel Drucker and Joel Habener showed that small amounts of lab-made GLP-1 could trigger insulin. Mojsov later fought to have her name included in the patents, and the hospital eventually amended four of them.
There was a catch. Natural GLP-1 is broken down so fast, mainly by an enzyme called , that its is only about two minutes. Used as it is, it was impossible to develop into a drug. That one problem set the agenda for what followed: researchers turned to the hormone's receptor instead of the hormone itself.
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Recap
GLP-1 is a gut hormone that talks to the pancreas, the stomach and the brain, but the body wipes it away within minutes.
💡 A trick to remember it · Gut sends a text after dinner: 'insulin up, stomach slow, brain full', and the text deletes itself in two minutes.
Surprising fact · Natural GLP-1 has a half-life of about two minutes, so researchers had to build longer-lasting look-alikes.
Connects to
- 💉 How do Ozempic, Wegovy, Mounjaro and Zepbound work?
- 📏 How is obesity defined, and why do people argue about BMI?
- 🧠 Does your gut really talk to your brain, and do microbes join the conversation?
- 💉 What does insulin actually do in your body?
- 🦠 What do the trillions of microbes in your gut actually do?
- Diabetes
Sources (2)
No source, no claim. Every fact in this lesson (13 claims) cites at least one of these.