SAN ANTONIO — May 5, 2026 – People who begin obesity treatment with glucagon-like peptide-1 receptor agonists (GLP-1s) and then undergo metabolic and bariatric surgery achieve substantially greater weight loss than with the medications alone, according to new research* presented today at the annual meeting of the American Society for Metabolic and Bariatric Surgery (#ASMBS2026).
Researchers from the NYU Grossman School of Medicine found patients treated with GLP-1 drugs, either semaglutide or tirzepatide, lost about 8% of their total body weight in the months prior to surgery. Total weight loss increased to more than 25% among those who later turned to gastric bypass surgery and about 20% among those who had sleeve gastrectomy. By comparison, patients who went directly to surgery lost about 2% to 3% more after their procedures, showing the GLP-1s did little to diminish their effectiveness.
"Patients are increasingly having surgery after GLP-1 therapy, making it important to understand how prior medical treatment may influence outcomes," said Karan R. Chhabra, MD, MSc, lead study author and Assistant Professor of Surgery and Population Health, NYU Grossman School of Medicine. "Our findings show that metabolic and bariatric surgery continues to deliver substantial and durable weight loss in this population."
The study analyzed electronic health records from more than 6,700 patients who had been prescribed GLP-1 medications in the six months before surgery, including 2,395 who underwent gastric bypass and 4,315 who had sleeve gastrectomy. Outcomes were compared with those of patients with no prior GLP-1 use, nearly 40,000 gastric bypass patients and more than 87,000 sleeve gastrectomy patients. Data from 2019 to 2025 were drawn from the Epic Cosmos database.
The study also found that patients who used GLP-1s before surgery were more likely to resume drug treatment afterwards though this was less likely among gastric bypass patients than those undergoing sleeve gastrectomy in the first year (44.1% vs. 57.4%). By three years, about two-thirds of all patients were back on GLP-1s. Researchers noted this suggests that initiating GLP-1 treatment before surgery may increase the likelihood of long-term or resumed use post-operatively, while patients who proceed directly to surgery may be less likely to require lifelong medication.
Metabolic and bariatric or weight-loss surgery, such as gastric bypass and sleeve gastrectomy, have been shown to be the most effective and long-lasting treatment for severe obesity. The operations improve or resolve diseases including type 2 diabetes, heart disease and high blood pressure and leads to significant and durable weight loss. Its safety profile is comparable to some of the safest and most commonly performed surgeries in the U.S., including gallbladder surgery, appendectomy and knee replacement.
"As the use of GLP-1 drugs continues to rise, it's critical that patients and providers understand how these treatments fit into the broader care pathway, particularly for individuals who may benefit from metabolic and bariatric surgery," said Richard M. Peterson, MD, MPH, FASMBS, President, ASMBS and Professor of Surgery at UT Health San Antonio in Texas, who was not involved in the study. "Medications may start the weight loss journey, but surgery remains the most effective and durable treatment for most patients with severe obesity."
According to the ASMBS, less than 1% of those eligible for weight-loss surgery currently have it in any given year. More than 270,000 bariatric surgeries were performed in 2023, the latest estimates available.
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