Bariatric surgery outperformed injectable GLP-1s in real-world weight loss study
The figures suggest injectable GLP-1 drugs deliver less weight loss in routine care than the 15% to 21% reported in clinical trials, which could shape what patients expect.
Researchers who compared thousands of patient records found that people who underwent sleeve gastrectomy or gastric bypass lost far more weight over two years than those who filled prescriptions for injectable GLP-1 drugs, according to results presented June 17, 2025 at the ASMBS 2025 Annual Scientific Meeting in Washington, DC [1].
The average surgical patient dropped 58 pounds by the two-year mark. Patients who had a GLP-1 prescription for at least six months lost an average of 12 pounds. In percentage terms, that is 24% total weight loss for surgery and 4.7% for the medication group [1]. Staying on treatment longer helped somewhat: patients on continuous GLP-1 therapy for a full 12 months averaged 7% total weight loss, still well below the surgical group [1].
The work came from NYU Langone Health and NYC Health + Hospitals. It was retrospective and drew on electronic medical records rather than assigning people at random to a treatment. It covered patients with a body mass index of at least 35 who either had sleeve gastrectomy or Roux-en-Y gastric bypass, or received a prescription for injectable semaglutide (sold as Ozempic and Wegovy) or tirzepatide (sold as Mounjaro and Zepbound) at some point between 2018 and 2024 [1]. Researchers compared 51,085 surgical and GLP-1 patients, using average treatment effect weighting to account for differences in age, BMI and coexisting conditions [1]. Funding came through an NYU CTSA grant, KL2 TR001446, from the National Center for Advancing Translational Sciences at the National Institutes of Health [1].
"Clinical trials show weight loss between 15% to 21% for GLP-1s, but this study suggests that weight loss in the real world is considerably lower even for patients who have active prescriptions for an entire year," said lead author Avery Brown, MD, a surgical resident at NYU Langone Health. "We know as many as 70% of patients may discontinue treatment within one year" [1]. Brown added that GLP-1 patients "may need to adjust their expectations, adhere more closely to treatment or opt for metabolic and bariatric surgery to achieve desired results" [1].
The paper did not split out results for semaglutide versus tirzepatide, and a molecule-by-molecule comparison has not been disclosed [1].
Why it matters for patients
Everyday results can look different from trial results, and this study suggests that pattern applies to GLP-1 medications. Time on treatment appears to be one factor: an average 7% loss after a full year of continuous therapy is modest next to the 15% to 21% range cited from clinical trials [1]. ASMBS also points to separate research finding that 53.6% of patients with overweight or obesity stopped GLP-1 therapy within a year, a share that climbs to 72.2% by two years [1]. About 12% of American adults say they have ever taken a GLP-1 drug, and 6% report being in treatment now [1].
Bariatric surgery, by contrast, reaches a small slice of people who qualify for it. ASMBS counts more than 270,000 metabolic and bariatric procedures in the United States in 2023, roughly 1% of those who meet eligibility requirements based on BMI [1]. The group describes the operations' safety profile as comparable to gallbladder surgery, appendectomy and knee replacement [1]. CDC figures cited by ASMBS put obesity prevalence at 40.3% and severe obesity at 9.4% [1].
Ann M. Rogers, MD, president of ASMBS, who was not involved in the research, said both groups lose weight but called surgery "much more effective and durable," adding that patients who get insufficient weight loss from GLP-1s, or who struggle to comply because of side effects or costs, "should consider bariatric surgery as an option or even in combination" [1].
Several questions remain open. The design cannot rule out differences between the two groups that the statistical adjustment missed. All patients came from one New York health system, and the authors did not report why the medication group lost less in practice, whether dosing, missed doses, insurance coverage, side effects or another factor was responsible [1]. Whether the findings hold for patients elsewhere has not been reported.
Karan R. Chhabra, MD, MSc, the senior author and an assistant professor of surgery and population health at NYU Grossman School of Medicine, said future analyses will examine how providers can improve GLP-1 outcomes, which patients do better with surgery versus medication, and how out-of-pocket costs affect treatment success [1]. No dates for those analyses have been announced.
Sources
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