GLP-1 Medications: How They Work, Side Effects, and Long-Term Considerations

GLP-1 medications have rapidly shifted from diabetes clinics to dinner table conversations. They’re often presented as a “silver bullet” for weight loss. But how true is this claim?

GLP-1 medications are drugs that reduce appetite, slow digestion, and affect hunger signals, originally developed for diabetes management and now also prescribed for weight loss.

In this three-part series, we’ll explore GLP-1 medications, including Wegovy, Mounjaro, and Ozempic.

In Part 1, we’ll explain what GLP-1 medications are and how they affect appetite and eating. In Parts 2 and 3, we’ll explore the relationship between GLP-1 medications, eating disorders, and intuitive eating.

What is GLP-1?

GLP-1 stands for glucagon-like peptide-1. It is a naturally occurring hormone released by the gut after eating. Its role is to help regulate blood sugar levels, appetite, and digestion.

GLP-1 medications mimic this hormone, enhancing its effects in the body. The active ingredients in these medications include semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro). While brand names differ, their effects on appetite and digestion are similar.

These medications have been used in clinical practice since 2005 and were originally developed to help manage type 2 diabetes. Ozempic was approved in 2017 for blood glucose management. During my time working in a diabetes clinic, there was significant excitement among clinicians about their effectiveness in supporting blood sugar regulation.

Their more recent use for weight loss has brought them into mainstream awareness.

How GLP-1 medications work

GLP-1 medications affect several systems in the body. Their three primary actions are:

1. Increasing insulin release

GLP-1 medications encourage the pancreas to release insulin when blood glucose levels are high. This helps lower blood sugar levels in a regulated and responsive way.

2. Slowing gastric emptying

These medications slow the movement of food from the stomach into the small intestine. This process, known as delayed gastric emptying, can mean people may feel fuller for longer.

However, this effect can also lead to side effects such as:

Nausea or feeling like you might be sick
Uncomfortable bloating
Constipation
Early fullness

Up to 50% of people taking GLP-1 medications experience nausea, particularly when starting the medication or increasing the dose. Imagine feeling your meal sitting in your stomach for longer than you’re used to - some people really dislike this side effect/feeling.

3. Affecting hunger and fullness signals in the brain

GLP-1 medications act on areas of the brain involved in appetite regulation. This can lead to:

reduced hunger
feeling full sooner
reduced interest in food
decreased “food noise”

As a result, many people eat smaller amounts and less frequently.

Less common but more serious risks include pancreatitis, gallbladder disease, and rare psychological side effects.

Appetite suppression isn’t always neutral

Appetite is one of the body’s primary ways of signalling energy needs. Hunger isn’t a flaw, it’s a protective mechanism that helps ensure we eat enough to support basic functioning, energy, and overall health.

Think about hunger the same way we think about the urge to pee. When we need to pee, we go. If a bathroom isn’t available, we might hold it temporarily. But we don’t shame ourselves for having the urge. We don’t view it as a failure of willpower.

Hunger, however, has been demonised. Many people are actively trying to override, delay, or silence it.

When appetite is suppressed, it can become harder to eat enough food to look after your body - sometimes without realising it. And over time, consistently under-fuelling can affect mood, energy, and health, potentially increasing the risk of inadequate intake and, in some cases, malnutrition.(1) We might see muscle loss, bone weakening, or vitamin & mineral deficiencies.

Long-Term Impacts of GLP-1

Current evidence suggests that weight loss achieved with GLP-1 medications is difficult to maintain once treatment stops. In a post-treatment analysis published in eClinicalMedicine, participants regained a substantial proportion of lost weight within one year of discontinuing the medication, reinforcing that these effects are largely dependent on taking the medication rather than permanent.(2)

GLP-1 medications are not inherently good or bad. Like any medical treatment, they have benefits, risks, and individual considerations. Understanding how they affect appetite and eating is an important part of informed decision-making.

For individuals with a history of disordered eating, chronic dieting, or high energy demands, these effects can be more complex. Reduced hunger cues may make it harder to maintain adequate and consistent nourishment.

This is explored further in Part 2 of this series, where we examine GLP-1 medications and eating disorder risk.

References

Fallows E. Malnutrition with use of GLP-1 agonists is an underestimated real-world harm. BMJ. 2025;390:r1512.
Jensen SBK, et al. Healthy weight loss maintenance with exercise, GLP-1 receptor agonist, or both combined followed by one year without treatment: a post-treatment analysis of a randomised placebo-controlled trial. eClinicalMedicine. 2024;69:102475.