Medical treatment or bariatric surgery: a new era in obesity treatment

What is medical treatment for weight loss?

Medical treatment involves using prescription medications to support weight loss. Today, these consist primarily of GLP-1 and GLP-1/GIP receptor agonists, which affect the body's biological regulation of appetite and satiety.

Medications such as semaglutide (Wegovy) and tirzepatide (Mounjaro) mimic or enhance the effect of the body's own intestinal hormones released in connection with meals. They act both peripherally, partly by delaying gastric emptying, and centrally by affecting the brain's appetite-regulating centres. Many experience reduced hunger and a decreased craving for energy-dense food.

To achieve long-term and safe results, treatment is recommended in combination with lifestyle changes, such as dietary adjustments and increased physical activity. Medical treatment is an important option for individuals with a BMI over 30, or over 27 in the presence of at least one weight-related comorbidity, especially when surgery is not appropriate or desired.

What does bariatric surgery involve? Gastric bypass, gastric sleeve, and duodenal switch

Bariatric surgery, or obesity surgery, refers to surgical procedures in the gastrointestinal tract used to treat obesity. The aim is to reduce energy intake and influence the body's hormonal regulation of appetite, satiety, and metabolism.

The most common methods are gastric bypass and gastric sleeve. In a gastric bypass, a small stomach pouch is created and connected directly to the small intestine, which both limits food intake and changes how nutrients are absorbed. In a gastric sleeve, a large portion of the stomach is surgically removed, reducing the stomach's volume and affecting hunger hormones such as ghrelin.

In addition to the mechanical effect, these procedures lead to significant hormonal changes in the gastrointestinal tract, which often reduce appetite and can provide rapid improvement in metabolic diseases such as type 2 diabetes.

An advanced method, used only in a few cases, is the duodenal switch, where a larger part of the small intestine is bypassed. This often results in greater weight loss but also involves an increased risk of complications and nutritional deficiencies, requiring careful medical follow-up.

How do the different treatment options work?

Bariatric surgery works through both anatomical and hormonal changes in the gastrointestinal tract, affecting food intake, satiety, and energy metabolism. Medical treatment, instead, works by mimicking the body's own satiety hormones and affecting appetite regulation via injections or tablets.

However, the goal of both methods is similar. Research shows that during weight loss, the body activates compensatory mechanisms, such as increased hunger and altered hormonal balance, which counteract continued weight loss.

Both modern medical treatment (GLP-1 and GLP-1/GIP receptor agonists) and bariatric surgery can counteract these mechanisms by influencing appetite regulation and energy balance. This often makes it easier to achieve and maintain clinically significant weight loss.

Effect on weight loss – what does the research say?

Research shows that the average weight loss with modern medications in some cases approaches the results previously achieved primarily through bariatric surgery. However, on average, surgery still provides a greater and more lasting weight loss.

The development of new medications, such as semaglutide (Wegovy) and tirzepatide (Mounjaro), has changed treatment possibilities. In large clinical studies, these medications have shown an average weight loss of approximately 15–20 per cent of body weight.

For some patients, this can enable clinically significant and sustainable weight loss through medical treatment combined with lifestyle support, without surgery necessarily having to be the first-choice option.

Advantages of medical treatment

Pharmacological treatment requires no surgery or recovery time associated with an operation. The dose can be titrated (adjusted) gradually, and treatment can be paused or ended if necessary, unlike surgical procedures which cannot be easily reversed. However, treatment often needs to be long-term to maintain the weight loss.

Modern medications have also shown positive effects on several cardiometabolic risk factors, such as blood sugar, blood pressure, and weight. Treatment is usually recommended in combination with lifestyle changes and clinical follow-up.

In some cases, medical treatment can also be used prior to surgery to reduce liver volume, thereby facilitating the operation and reducing risks.

Advantages of bariatric surgery

Bariatric surgery often leads to significant and lasting weight loss and can provide rapid improvement – and in some cases, remission – of type 2 diabetes, sometimes even before major weight loss has occurred.

For individuals with severe or morbid obesity, where medication or lifestyle interventions have not had sufficient effect, surgery can be an important and, in some cases, life-saving treatment.

The anatomical changes in the gastrointestinal tract limit the amount of food that can be consumed, especially initially after the operation, and contribute alongside hormonal changes to reduced appetite and improved metabolic control. This can facilitate long-term lifestyle changes.

Risks and side effects to be aware of

Following bariatric surgery, the patient needs regular follow-up and must take vitamin and mineral supplements, such as vitamin B12, iron, calcium, and vitamin D, as the absorption of certain nutrients can be affected. Dumping syndrome can occur after gastric bypass, where food passes too quickly into the small intestine, causing symptoms such as nausea, palpitations, and sweating. Surgical complications can include bleeding, infection, and leakage.

Medical treatment can cause side effects such as nausea, diarrhoea, and constipation. These are most common at the start of treatment and can often be alleviated through gradual dose increases.

Both forms of treatment can involve a risk of muscle mass loss in connection with rapid weight loss. It is therefore important that treatment is combined with sufficient protein intake and regular strength training.

The future of obesity treatment

The future of obesity treatment is increasingly moving towards pharmacological innovations and more individualised care, where medications affecting multiple hormonal signalling pathways may play an ever-greater role.

Modern medications, such as semaglutide and tirzepatide, have already shown good efficacy, even in patients who have previously undergone bariatric surgery and who experience insufficient weight loss or weight regain after the operation.

New generations of medications, including oral alternatives and so-called triple agonists (e.g., GLP-1/GIP/glucagon), are being evaluated in clinical studies and have shown potential in early results for further improved weight loss.

At the same time, bariatric surgery remains the most effective treatment for significant and lasting weight loss at a group level. Future treatment strategies will likely combine pharmacological and surgical methods to a higher degree, where the choice of treatment is individualised based on the patient's risk profile, treatment response, and preferences.

Frequently asked questions about medical treatment and surgical treatment

Which treatment gives the greatest weight loss – medical treatment or surgery?

Bariatric surgery is still the most effective treatment for large and lasting weight loss at a group level. However, modern medications such as semaglutide and tirzepatide can provide significant weight loss and, in some cases, approach surgical results, making medical treatment a very important alternative or complement to surgery today.

Medical treatment does not involve surgery and can be adapted or ended over time, but it has its own side effects and often requires long-term treatment. The choice of treatment should therefore be based on an individual medical assessment.

Can the treatments be combined?

Yes. In clinical practice, it is common to combine bariatric surgery with medical treatment if necessary. Medications such as semaglutide or tirzepatide can be used after surgery, for example, in cases of weight regain or insufficient weight loss.

The combination can also be relevant prior to surgery, where medical treatment is used to reduce weight and liver size before the operation.

Treatment should always take place under medical supervision to ensure correct dosage and optimal treatment results.

How long does it take to see results?

With bariatric surgery, weight loss often occurs rapidly, especially during the first months after the operation. Thereafter, the weight loss usually plateaus, and some weight regain may occur over time, although many maintain a significant portion of their weight loss in the long term.

With medical treatment, weight loss occurs more gradually. Many patients begin to see an effect within the first few months, and the weight thereafter continues to decrease successively over time as the dose is optimised and the body adapts to the treatment.

What risks are associated with the treatments?

Bariatric surgery involves risks of surgical complications, such as infection, bleeding, and leakage, as well as long-term effects like dumping syndrome and nutritional deficiencies requiring lifelong follow-up and vitamin/mineral supplements.

Medical treatment has a different and less invasive risk profile but can cause side effects, primarily from the gastrointestinal tract, such as nausea, diarrhoea, and constipation. These are most common at the start of treatment. In rare cases, other side effects may occur, such as gallstone issues or inflammation of the pancreas.

The choice of treatment should always be based on an individual medical assessment where the benefits are weighed against the risks.

Sources

Wilding JPH et al. (STEP 1 Trial). Once-Weekly Semaglutide in Adults with Overweight or Obesity. The New England Journal of Medicine.
https://www.nejm.org/doi/full/10.1056/NEJMoa2032183

Jastreboff AM et al. (SURMOUNT-1 Trial). Tirzepatide Once Weekly for the Treatment of Obesity. The New England Journal of Medicine.
https://www.nejm.org/doi/full/10.1056/NEJMoa2206038

Sjöström L et al. Effects of Bariatric Surgery on Mortality in Swedish Obese Subjects. The New England Journal of Medicine.
https://www.nejm.org/doi/full/10.1056/NEJMoa066254

Arterburn DE & Courcoulas AP. Bariatric Surgery for Obesity and Metabolic Conditions in Adults.
https://pubmed.ncbi.nlm.nih.gov/25164369/

European Medicines Agency (EMA). Wegovy
https://www.ema.europa.eu/en/medicines/human/EPAR/wegovy

European Medicines Agency (EMA). Mounjaro
https://www.ema.europa.eu/en/medicines/human/EPAR/mounjaro