A new real-world comparison finds that bariatric surgery leads to dramatically more weight loss than popular injectable medications. After two years, people who underwent sleeve gastrectomy or gastric bypass lost about five times more weight than those using weekly GLP-1 receptor agonists such as semaglutide or tirzepatide,* according to research presented at the American Society for Metabolic and Bariatric Surgery (ASMBS) 2025 Annual Scientific Meeting.

The study, conducted by researchers at NYU Langone Health and NYC Health + Hospitals, showed that surgery patients lost an average of 58 pounds over two years. In contrast, patients who were prescribed a GLP-1 drug for at least six months lost about 12 pounds. That translates to 24% total weight loss for surgery patients compared with 4.7% for those using medication. Even among patients who stayed on GLP-1 therapy continuously for a full year, average weight loss reached only 7%, still far below the results seen with surgery.

Real-World Results Fall Short of Clinical Trials

"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. We know as many as 70% of patients may discontinue treatment within one year," said lead author Avery Brown, MD, a surgical resident at NYU Langone Health. "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."

The findings highlight a key gap between controlled clinical trials and everyday use, where side effects, costs, and long-term adherence can limit the effectiveness of medication-based weight loss.

How the Study Compared Surgery and GLP-1 Medications

Researchers analyzed electronic medical record data from patients treated between 2018 and 2024 within the NYU Langone Health and NYC Health + Hospitals systems. All participants had a body mass index (BMI) of at least 35 and either underwent bariatric surgery (sleeve gastrectomy or Roux en-Y gastric bypass) or received a prescription for injectable semaglutide or tirzepatide.

After adjusting for factors such as age, BMI, and co-morbidities using average treatment effect weighting, the team compared outcomes for 51,085 patients across both groups. The study was supported by NYU CTSA grant KL2 TR001446 from the National Center for Advancing Translational Sciences at the National Institutes of Health (NIH).

Future Research and Treatment Decisions

"In future studies we will aim to identify what healthcare providers can do to optimize GLP-1 outcomes, identify which patients are better treated with bariatric surgery versus GLP-1s, and determine the role out-of-pocket costs play in treatment success," said senior author Karan R. Chhabra, MD, MSc, a bariatric surgeon and Assistant Professor of Surgery and Population Health at NYU Grossman School of Medicine.