Modern medical treatment of overweight and obesity with GIP and GLP-1 analogues – What happens in your body

New possibilities with better conditions

Obesity is a chronic and complex disease influenced by a combination of genetics, hormones, lifestyle and environment. This means that the condition cannot be explained by lifestyle choices alone. The advice to “eat less and move more” therefore rarely leads to sustainable change.

In recent years, modern weight-loss medications have become true game changers, genuinely transforming how we can treat severe overweight and obesity. With medicines developed by companies such as Novo Nordisk (for example semaglutide in Ozempic, Wegovy and Rybelsus, and liraglutide in Saxenda) and Eli Lilly (for example dulaglutide in Trulicity and tirzepatide in Mounjaro), people now have better conditions for making the lifestyle changes needed to lose weight and maintain a lower weight.

How modern weight-loss medications work

The most commonly used medicines today are so-called GLP-1 analogues and combined GLP-1 and GIP analogues. They mimic the body’s own satiety hormones, which are released after a meal and help regulate appetite and blood sugar. The medication slows stomach emptying and also affects how hunger and satiety are regulated in the brain. As a result, many people experience reduced “food noise” and find it easier to resist cravings. Altogether, this makes it easier to eat less and make more conscious food choices, which can lead to lower energy intake and consequently weight loss.

How quickly can you expect results?

How quickly the medication starts to work varies from person to person. Some notice a difference from the first day, while it may take several weeks for others. Generally, it takes 4–8 weeks for the level of the medicine in the body to stabilise. The effects may still vary somewhat, but not as much as at the beginning of treatment.

Possible side effects

The most common side effects are gastrointestinal issues such as nausea, constipation, diarrhoea and heartburn. Some people may also experience increased tiredness and headaches. These symptoms are usually mild and temporary. They can often be prevented by starting with a low dose and increasing gradually if needed, as well as by paying attention to how one eats during treatment.

Use during pregnancy or before surgery

Weight-loss medications should not be used during pregnancy. If you are planning to become pregnant, or if you become pregnant while on treatment, the medication must be discontinued. Treatment should be stopped at least two months before attempting to conceive, as the body takes a long time to break down and eliminate the substance. Because a potential risk to a breastfed infant cannot be ruled out, the medication should also not be used while breastfeeding.

Before surgery, it is important to inform healthcare staff if you are taking these medicines, as they affect how quickly the stomach empties. This matters because patients must be fasting before anaesthesia.

How much weight loss can you expect?

Large clinical studies have shown that modern weight-loss medications lead to an average weight loss of 15–20% of body weight (2,3) – a level previously only achievable mainly through bariatric surgery.

The amount of weight lost varies between individuals and depends on several factors, including starting weight, how the body responds to treatment and how well lifestyle changes are implemented. Everyone responds differently, and weight-loss journeys are individual, so it is helpful to focus on one’s own progress rather than comparing with others.

More than just weight loss

The benefits of obesity medications extend beyond the number on the scales. Even a modest 5–10% weight loss can bring major health improvements, such as better blood sugar control, improved triglyceride levels and lower blood pressure – all of which are risk factors for future cardiovascular disease (4). The more weight lost, the greater the effects.

• Blood sugar decreases, and type 2 diabetes may even go into remission.
• Blood fats and liver values improve – fatty liver can even heal.
• Blood pressure drops, reducing the risk of cardiovascular disease.
• Symptoms of PCOS, asthma, sleep apnoea and osteoarthritis can improve.

The medications also appear to reduce cravings for alcohol and nicotine, opening the door to broader future uses. In addition, they have shown positive effects on quality of life, energy levels and body composition, including reductions in visceral fat around organs such as the liver and pancreas.

View the medicine as support – not the whole solution

Although the medication provides strong support and, for many, a long-awaited missing piece of the weight puzzle, it does not do all the work on its own. Personal effort plays a crucial role in determining the results. Weight loss always requires an energy deficit – consuming fewer calories than the body uses. The medicine helps with this and provides better conditions for success, but most people will still need to actively work on changing their habits.

Common questions and answers about GIP and GLP-1 analogues

Is hunger abnormal during treatment?

Hunger is an important signal from the body that ensures we get enough energy and nutrients to function optimally. The medication can reduce appetite so that hunger decreases, but it does not disappear completely. Feeling hungry is therefore normal – even during treatment.

If you experience strong hunger despite following the dietary advice you have received, it may be worth discussing with your doctor whether your dose should be adjusted, whether you should switch medication or whether the treatment should be combined with other medicines.

Does the effect diminish over time?

After some time on treatment, many people experience an increase in hunger and worry that the medication has stopped working. This is usually not due to a loss of effect but rather the body’s own defence against weight loss, known as metabolic adaptation (5). This involves, among other things, a reduction in energy expenditure and an increase in hunger signals.

This is a valuable survival instinct during starvation – but something that makes it difficult for us to maintain weight loss, especially in a society where food is available everywhere and around the clock.

What happens when you reach your target weight?

When the target weight has been reached, many people try a “maintenance dose”, meaning the lowest dose needed to maintain the results and keep weight stable. There is currently no scientific evidence regarding how long treatment can be continued without risking weight regain. For many, it is likely to be lifelong, and any reduction or discontinuation of the medication should always be done in consultation with a doctor.

What happens if you stop taking the medication?

Research clearly shows that if treatment is stopped completely, weight tends to increase again (6,7). This reinforces the understanding of obesity as a chronic and complex disease – not a result of weak willpower or lack of discipline. After weight loss, the body will naturally strive to return to its previous highest weight (the so-called set point).

‍No shortcut – but a new path

Needing medication to lose weight and maintain a lower weight is nothing to be ashamed of. It is neither a sign of weakness nor failure, and it has nothing to do with a lack of willpower or character. On the contrary, it is an important part of treating a complex disease.

At times, however, the medication can be difficult to access due to shortages, which may affect treatment options.

With modern medicines, we have taken an important step forward in treating severe overweight and obesity. The treatment increases the chances of maintaining the new, lower weight and preserving the health benefits that have been achieved – something that reduces the risk of ill health and disease. And development is moving quickly: new generations of medicines are already on the way, offering even greater effectiveness and fewer side effects.

Summary

Obesity is a complex disease influenced by genetics, hormones, lifestyle and environment. For many people, lifestyle changes alone are not enough to achieve weight loss and maintain it.

New medications from Novo Nordisk (such as Wegovy, Ozempic and Rybelsus) and Eli Lilly (such as Mounjaro and Trulicity) mimic the body’s own satiety hormones and help reduce appetite and increase feelings of fullness. This makes it easier to eat less and achieve the energy deficit needed for weight loss.

Side effects are usually mild and most common at the beginning of treatment. It is also important to remember that the medication is a support on the journey towards better health – it works best together with sustainable lifestyle changes.

References

1. World Health Organization (2024). Obesity and overweight. https://www.who.int/news-room/fact-sheets/detail/obesity-and-overweight [2025-09-13].
2. Wilding, J.P.H. et al., (2021). Once-weekly semaglutide in adults with overweight or obesity. New England Journal of Medicine, 384(11), pp.989–1002.
3. Jastreboff, A. M., Aronne, L. J., Ahmad, N. N., Wharton, S., Connery, L., Alves, B., Kiyosue, A., Zhang, S., Liu, B., Bunck, M. C., Stefanski, A., & SURMOUNT-1 Investigators (2022). Tirzepatide Once Weekly for the Treatment of Obesity. The New England journal of medicine, 387(3), 205–216.
4. Ryan, D. H., & Yockey, S. R. (2017). Weight Loss and Improvement in Comorbidity: Differences at 5%, 10%, 15%, and Over. Current obesity reports, 6(2), 187–194.
5. Ard, J., Fitch, A., Fruh, S. and Herman, L. (2021). Weight loss and maintenance related to the mechanism of action of glucagon-like peptide 1 receptor agonists. Advances in Therapy, 38(6), pp.2821-2839.
6. Wilding, J. P. H., Batterham, R. L., Davies, M., Van Gaal, L. F., Kandler, K., Konakli, K., Lingvay, I., McGowan, B. M., Oral, T. K., Rosenstock, J., Wadden, T. A., Wharton, S., Yokote, K., Kushner, R. F., & STEP 1 Study Group (2022). Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes, obesity & metabolism, 24(8), 1553–1564.
7. Aronne, L. J., Sattar, N., Horn, D. B., Bays, H. E., Wharton, S., Lin, W. Y., Ahmad, N. N., Zhang, S., Liao, R., Bunck, M. C., Jouravskaya, I., Murphy, M. A., & SURMOUNT-4 Investigators (2024). Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA, 331(1), 38–48.

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