Popular weight loss injections like Wegovy and Mounjaro may not deliver the dramatic results seen in clinical trials when used in everyday settings, new research suggests.
These medications, part of a class known as GLP-1 receptor agonists (GLP-1 RAs), have gained popularity for their obesity treatment. Clinical studies show they can help patients shed up to 20% of their body weight over 72 weeks.
However, a new study led by Dr Karan Chhabra of New York University’s Grossman School of Medicine found that real-world patients lose far less weight on these jabs compared to clinical trial results or bariatric surgery.
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“The average patient on GLP-1 RAs in the real world is not getting the weight loss that we see in clinical trials,” said Dr Chhabra.
The researchers analysed data from more than 51,000 patients who were eligible for bariatric surgery or weight-loss medication. They compared outcomes between 38,545 people who were prescribed semaglutide or tirzepatide and 12,540 patients who underwent weight loss surgery across a period of up to three years.
The team found that bariatric surgery patients lost an average of 26.5 per cent of body weight after two years, while GLP-1 RA patients lost only 5.7% on average. “The most reliable way to lose 20% to 30% of your weight is to get a bariatric operation,” Chhabra said.
GLP-1 RAs may have a smaller real-world impact due to factors such as treatment cost, inconsistent long-term use, dose management, or side effects. Patients may also stop treatment early, which may explain why trial results don’t always align with real-world outcomes.
Experts say further research is needed to help patients achieve the best outcomes with these medications. “Our goal is to get as many people to the right treatment as possible,” Chhabra said. “But patients need to know what to realistically expect.”
The findings, which will be presented at the American Society for Metabolic and Bariatric Surgery 2025 annual meeting, are not yet peer-reviewed.
