What is GLP-1?

Thursday 2nd July

GLP-1 is short for glucagon-like peptide-1. It’s a hormone, one of the chemical messengers your body uses to send signals from one place to another. You make it yourself, every day, in your gut. It’s a completely natural part of how your digestive system talks to the rest of your body.

Think of GLP-1 as one of the messengers your gut sends out after you eat. When food arrives, specialised cells lining your intestine release it into the bloodstream, where it helps coordinate what happens next: how your body handles the energy from your meal, and how full you feel.

Where does it come from?
GLP-1 is made by special cells in the lining of your small intestine and colon, known as L-cells. These are part of a much bigger system: the gut is the largest hormone-producing organ in the body, quietly releasing dozens of signals as food passes through, controlling food signals, hunger and appetite and energy levels.

These L-cells sit there waiting, and when the food you’ve eaten reaches them, they respond by releasing GLP-1. At rest, levels are low; after a meal, they rise, then settle again. It’s a normal daily rhythm that’s been going on inside you your whole life, long before anyone gave the hormone a name. (Scientists first identified GLP-1 in the 1980s, after mapping the gene it comes from.)

A quick sense of scale
When you haven’t eaten for a while, the active form of GLP-1 in your blood sits at a low baseline. After a meal, it can rise to roughly two to three times that level, with the exact amount depending on how big the meal is and what it contained. In other words, eating is the natural trigger, and your body is designed to respond.

What does GLP-1 actually do?
GLP-1 is a natural hormone your gut makes after you eat, and it helps with feeling full, the pace of digestion, and steady blood sugar. Researchers describe it as a “gut-brain” hormone because it helps your digestive system and your brain stay in conversation about food and energy. Its best-understood natural roles include:

Helping you feel full. GLP-1 is one of the signals involved in satiety, the comfortable feeling of having had enough to eat. It’s part of how your body knows a meal has landed.

Slowing the pace of digestion. It helps regulate how quickly your stomach empties, so the contents of a meal move through at a steady rate rather than all at once.

Helping manage blood sugar. GLP-1 is what scientists call an “incretin” hormone. After you eat, it helps your body release insulin in response to rising blood sugar, part of keeping your energy on an even keel between meals.

All of this happens automatically. You don’t feel GLP-1 being released any more than you feel any other hormone; it works in the background as part of normal digestion.

GLP-1 and the science of feeling full
Hunger and fullness aren’t just about willpower, they’re managed by a web of hormones, of which GLP-1 is one. After a meal, a mix of these messengers travels to the brain’s appetite centres and helps bring the meal to a natural close. It’s an elegant system, and it’s the same in all of us, whether we ever think about it or not.

This is also why how you eat, not just how much, can affect how satisfied you feel. The body responds differently to different kinds of food and to the speed and size of a meal. That’s ordinary physiology, and it’s where everyday nutrition comes in.

Nutrition and your natural fullness signals
Your gut responds to eating, that’s its job. Different foods are digested at different speeds and in different ways, which is part of why some meals leave you feeling satisfied for hours while others seem to disappear without trace. None of this requires anything special; it’s how a balanced diet naturally works with your body. A few well-established principles:

Protein tends to be satisfying
Protein is generally the most filling of the three main macronutrients, and meals built around a good source of it often help people feel satisfied. Everyday sources include lean meat and poultry, fish, eggs, dairy, beans, lentils, tofu and other pulses.

Fibre helps a meal go further
Fibre adds bulk and slows digestion, which is part of why fibre-rich meals tend to feel more substantial. It also feeds the friendly bacteria in your gut. Most of us in the UK fall short of the recommended 30g of fibre a day. Good sources include wholegrains, oats, beans and pulses, fruit, vegetables, nuts and seeds.

Whole, less-processed foods give your gut more to work with

Foods closer to their natural state, vegetables, fruit, wholegrains, pulses, generally take longer to eat and digest than highly refined ones, which is part of why they tend to feel more satisfying. Building meals around them is one of the simplest, most reliable nutrition habits there is.

Slow down and let the signals catch up
Your fullness signals take a little time to register, often around 20 minutes. Eating at a relaxed pace gives your body the chance to recognise it’s had enough, which is why wolfing a meal can leave you feeling stuffed shortly afterwards.

The simple takeaway
You don’t need to “do” anything to your hormones. Eating balanced meals with enough protein and fibre, built around whole foods, and eating at a relaxed pace, is simply working with the system your body already has.

The bottom line
GLP-1 is a natural hormone, made in your gut, that helps with fullness, the pace of digestion and steady blood sugar. It’s part of the everyday machinery of being human, quietly doing its job every time you eat. Understanding it is a nice reminder that a lot of what keeps us feeling well is already built in, and that the basics of good nutrition, balanced meals, enough protein and fibre, mostly whole foods, are there to work alongside it.

A note on this article
This article is for general information and education only. It is not medical, dietary or nutritional advice, and it is not about any medicine or treatment. If you have questions about your health, weight or diet, or about any medication, speak to your GP, pharmacist or a registered dietitian.

Sources
Written from peer-reviewed and authoritative sources on the physiology of GLP-1 and on everyday nutrition. Key references:

Müller TD et al. Glucagon-like peptide 1 (GLP-1). Molecular Metabolism, 2019 – overview of GLP-1 physiology.

Holst JJ. The physiology of glucagon-like peptide 1. Physiological Reviews, 2007.

Gribble FM & Reimann F. Function and mechanisms of enteroendocrine cells (L-cells) in the gut. Annual Review of Physiology, 2016.

Marathe CS et al. Effects of GLP-1 on gastrointestinal motor function. Experimental Diabetes Research, 2011.

Tolhurst G et al. Short-chain fatty acids stimulate GLP-1 secretion via FFAR2. Diabetes, 2012.

NHS – How to get more fibre into your diet, and Eat well guidance (nhs.uk).

British Nutrition Foundation – Protein and Fibre resources (nutrition.org.uk).