How GLP-1 medications actually work

If you have seen Mounjaro and Wegovy described as "the skinny jab" you have already been misled. They are not amphetamines. They are not appetite suppressants in the old sense. They are carefully engineered analogues of your body's own gut hormones, and the reason they work is that they fix several different problems at once in a way that diet and willpower alone cannot.

Understanding the mechanism is worth ten minutes of your time, because it changes what you expect from treatment, how you use it, and how you stop.

What GLP-1 and GIP actually are

GLP-1 (glucagon-like peptide-1) is a hormone your small intestine releases when you eat. It does three things at once: it tells your pancreas to release the right amount of insulin, it slows the rate at which your stomach empties, and it signals fullness to your brain. GIP (glucose-dependent insulinotropic polypeptide) is a closely related gut hormone that does broadly similar work with a stronger metabolic effect.

In people without diabetes, these hormones peak shortly after a meal and fade away within a couple of hours. In people with obesity or type 2 diabetes, research has shown that the GLP-1 response is often blunted. You finish eating, but the signals that should say "enough now" are quieter than they should be. You do not feel full when a reasonable amount of food has been consumed, and you start feeling hungry again sooner than someone with a normal hormonal profile.

What the medications do

Semaglutide (the active ingredient in Wegovy and Ozempic) is a GLP-1 receptor agonist. It attaches to the same receptors as your natural GLP-1 but has been modified so that your body does not break it down for a week at a time. One weekly injection keeps GLP-1 signalling steadily elevated throughout the week.

Tirzepatide (Mounjaro) is a dual agonist. It attaches to both GLP-1 receptors and GIP receptors. The dual action produces stronger effects than GLP-1 alone and explains why Mounjaro has shown greater average weight loss than Wegovy in head-to-head studies.

Both drugs keep the hunger and satiety system turned up to normal levels consistently, rather than the low, spiky signalling that contributes to obesity.

The three things you will feel

Patients describe the experience of being on a well-titrated dose in three consistent ways.

Food noise quiets down. The background thinking about what to eat next, the planning for the next snack, the feeling of wanting something between meals, all fade in intensity. For many people this is the most striking change and the one that matters most psychologically. It is not about willpower. The neurological volume has changed.

Portions shrink naturally. Because the stomach empties slower, you feel full earlier in a meal. A plate that would previously have been finished without thought becomes too much after two-thirds. This is not starvation; it is appropriate satiety occurring at appropriate quantities.

Sweet and fatty foods lose their pull. Patients often report that rich or highly-processed foods no longer taste as appealing. This is partly because of the slower gastric emptying and partly because of changes in reward-system signalling. Some patients find themselves spontaneously preferring simpler, protein-rich meals.

What the medication does not do

It does not burn fat directly. It does not raise your metabolism substantially. It does not build muscle. Weight loss on GLP-1 medication is a consequence of eating less, typically 500 to 800 fewer calories per day, maintained consistently over months.

It does not fix the underlying biology permanently. Stopping the medication generally brings food noise and appetite back to baseline within weeks. Maintaining weight after stopping requires established habits, often supported with a lower maintenance dose.

It does not work equally for everyone. About 15 percent of patients are "non-responders" who lose less than 5 percent of body weight even at maximum dose. We screen for this before prescribing and have a clear plan for switching or stopping if it applies.

Why this matters for your treatment plan

Because GLP-1 medications work by normalising appetite hormones, the treatment sits alongside lifestyle change rather than replacing it. Your time on medication is your opportunity to rebuild habits around food that can persist once the medication is tapered or stopped.

At LoveMyLife we build this into the care plan. Your monthly reviews include not just dose adjustment and side-effect monitoring but practical conversation about what you are eating, how the new satiety feels, and what habits are becoming possible that were not possible before. The medication creates the window. The work during the window is what makes the weight stay off.

The honest bottom line

GLP-1 medications are the most effective pharmacological treatment for obesity ever developed. They work because they replace an understimulated signalling pathway. They are safe for most people when prescribed appropriately. They are not a cheat code, and the weight loss they produce is earned through eating less, not metabolically conjured.

If the above describes the problem you have been experiencing, an assessment is worth it.

Ready to start?

If this article has made you think medication might help, the next step is a short consultation with one of our weight-management doctors.

Begin your consultation at this link. Online in 30 minutes, or in person at Westfield London.