RWD study shows bariatric surgery leads to significantly greater weight loss than GLP-1 drugs

A new real-world study conducted by researchers from NYU Langone Health and NYC Health + Hospitals has found that bariatric surgery resulted in five-times more weight loss than GLP-1 drugs over 2 years, highlighting the need to reassess treatment expectations and strategies.

Using electronic health record (EHR) data from more than 51,000 patients with a body mass index (BMI) of at least 35, the study showed that bariatric surgery patients lost an average of 24% of their body weight (approximately 58 lbs) after 2 years, compared to just 4.7% (12 lbs) among those who received GLP-1 prescriptions for at least 6 months. Even among patients who remained on GLP-1 therapy for a full year, the average weight loss was only 7%.

The study, presented at the American Society for Metabolic and Bariatric Surgery (ASMBS) 2025 Annual Scientific Meeting, adjusted for age, BMI, and comorbidities using average treatment effect weighting. It was supported by NYU’s CTSA grant KL2 TR001446 from the National Center for Advancing Translational Sciences at the National Institutes of Health (NIH).

“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 study author Dr Avery Brown, a surgical resident at NYU Langone Health. He highlighted 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.”

GLP-1 receptor agonists, marketed as Ozempic and Wegovy (semaglutide), or Zepbound and Mounjaro (tirzepatide), have gained widespread use for weight management. However, real-world adherence remains a challenge. A recent study cited by the authors found that 53.6% of patients discontinued GLP-1 therapy within 1 year, and 72.2% had stopped by 2 years. According to survey data, around 12% of Americans have used a GLP-1 drug, including 6% who say they are currently in treatment.

Meanwhile, utilization of bariatric surgery remains low despite its demonstrated effectiveness. In 2023, just over 270,000 metabolic and bariatric procedures were performed in the US, representing fewer than 1% of individuals who meet eligibility criteria based on BMI, according to ASMBS.

ASMBS President Dr Ann M Rogers, who was not involved in the study, stated:

“While both patient groups lose weight, metabolic and bariatric surgery is much more effective and durable. Those who get insufficient weight loss with GLP-1s or have challenges complying with treatment due to side effects or costs, should consider bariatric surgery as an option or even in combination.”

Senior study author Dr Karan R Chhabra, Assistant Professor of Surgery and Population Health at NYU Grossman School of Medicine, noted that:

“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.” 

This study adds to a growing body of real-world evidence research evaluating the effectiveness of GLP-1s outside of clinical trial settings. As use of these therapies expands, so too does the volume of real-world data being generated to understand patient outcomes, adherence patterns, and comparative effectiveness. These insights are playing an increasingly important role in shaping clinical decisions and informing treatment guidelines.