How GLP-1 Medications Actually Work: The Science Made Simple

Although these medications are often called GLP-1s, this is really shorthand. The full, medical term for these medications is 'GLP-1 receptor agonists'. What does this actually mean? Well, all cells have receptors on them. These are little proteins on the surface of the cell that, when stimulated by something, such as a hormone, produce an effect in the cell.

'Agonist' just means that it stimulates the receptor. Receptors are essentially one of the main ways parts of the body communicate with each other. They send out chemical messengers, like hormones, that attach to the receptors on cells in other parts of the body. You can think of it like a hormone is a letter containing important information that someone sitting in one house wants to get to someone sitting in another house, and the receptor is like the letterbox in the person's front door that the letter is delivered through.

So the GLP-1 hormone that our body naturally produces acts on the GLP-1 receptor and stimulates it. At a molecular level, these weight loss drugs look similar to the GLP-1 hormone our bodies naturally make, so they can attach to the GLP-1 receptor and trick it into being stimulated. When the receptor is stimulated, it triggers a number of different effects in the body, including making us feel full.

These receptors are found in various places in the body. They are found on the cells in the pancreas, an organ that is involved in secreting insulin. Stimulating the GLP-1 receptor here increases insulin secretion and suppresses glucagon release, helping to stabilise blood glucose levels.

The GLP-1 receptor is also found in the cells in the gastrointestinal tract. Stimulating these slows down the speed at which food moves through the stomach. They are also found in the arcuate nucleus in the brain. This part of the brain is involved in appetite regulation and metabolism, so stimulating these here increases the feelings of fullness.

Interestingly, these receptors are also located in key areas of the brain's reward pathway. Activation of the GLP-1 receptor with GLP-1 medications in these reward centres can reduce the amount of dopamine released, so the reward pathways become less stimulated and these foods stop being so enjoyable.

This is a really important point to emphasise: lots of food choices that people struggling with their weight are making are based on trying to stimulate this reward pathway, rather than what their body actually needs. GLP-1 medications help break this cycle by allowing people to feel more in control of their eating and make rational choices about what they eat. For the first time, many people find they can think clearly about food and make decisions based on what's good for them, rather than being driven by cravings they can't control.