A real-world study recently published in Obesity found that bariatric surgery may confer greater long-term weight loss than semaglutide or tirzepatide for adults with obesity, with the researchers saying the findings “don’t argue against GLP-1s; they argue for transparent discussions and for keeping surgery on the table as a highly effective option for eligible patients”, reports Healio.
Karan Chhabra, MD, MSc, Assistant Professor of Surgery and Population Health at NYU Grossman School of Medicine, said previous studies comparing weight loss with GLP-1 receptor agonists to bariatric surgery tended to be indirect comparisons or include older GLP-1s.
Additionally, he said, weight loss in clinical trials for obesity drugs tends to be much higher than what healthcare professionals see from patients in a real-world setting.
In a retrospective analysis conducted at two health centres in the New York City region, researchers compared weight loss for adults with obesity (BMI 35 kg/m2) receiving medical therapy with injectable semaglutide (Ozempic/Wegovy, Novo Nordisk) or tirzepatide (Mounjaro/Zepbound, Eli Lilly) vs. bariatric surgery.
“The real-world weight loss from GLP-1s fell well short of both the clinical trial results and surgery,” Chhabra told Healio. “After two years, patients lost about 6.5% of their body weight on semaglutide and 10.8% on tirzepatide … vs. roughly 22% after sleeve gastrectomy and 28% after gastric bypass. In everyday practice, these drugs delivered only about one-third to one-half of what patients achieved with surgery. The real story isn’t drugs vs. surgery; it’s trial vs. reality.”
Adults who used an obesity drug had to use it continuously for at least one year to be included in the study. Weight loss was assessed at one, two and three years.
From 2018 to 2024, there were 10 913 adults who underwent bariatric surgery and 33 112 who started using semaglutide or tirzepatide. Those who underwent surgery were younger (P < .001) and had a higher mean BMI (43 kg/m2 vs. 40 kg/m2) than the medication group.
Weight loss
In weighted analysis, weight loss at one year was 25.6% for adults undergoing bariatric surgery and 6% for those receiving medication. At two years, the bariatric surgery group had 23.6% weight loss compared with 6.9% weight loss with medication.
Weight loss at three years with bariatric surgery was 23.5% compared with 7.8% with semaglutide or tirzepatide.
Gastric bypass was linked to the largest weight loss at 29.8% at one year, 28.1% at two years and 28.4% at three years. Sleeve gastrectomy conferred a 24.4% weight loss at one year, 22.4% at two years and 22% at three years. Weight loss with tirzepatide was 9.1% at one year and 10.8% at two years.
Semaglutide was linked to the lowest weight loss at 7.2% at one year, 8% at two years and 8.8% at three years.
The higher amount of weight loss with bariatric surgery compared with medications was observed both in adults with diabetes and those without diabetes.
HbA1c change
In weighted analysis, medical therapy conferred a larger decrease in HbA1c than bariatric surgery. Change in HbA1c at one year was –0.64 percentage points with semaglutide and –0.88 percentage points with tirzepatide compared with –0.56 percentage points with sleeve gastrectomy and –0.52 percentage points with gastric bypass.
At two years, HbA1c decreased by 0.76 percentage points from baseline with semaglutide, 0.67 percentage points with tirzepatide, 0.69 percentage points with sleeve gastrectomy and 0.52 percentage points with gastric bypass.
Chhabra said the findings show it is important for healthcare professionals to discuss real-world weight-loss expectations with patients and consider both surgery and medications as options for those with severe obesity.
“These findings don’t argue against GLP-1s; they argue for transparent discussions and for keeping surgery on the table as a highly effective option for eligible patients rather than treating medications as a default,” he said.
Chhabra added that it was noteworthy to see the large difference in weight loss between the trials and real-world settings, and future studies should examine how to improve care and reduce that gap.
“We also need longer-term follow-up on the safety profile of each treatment strategy, which we couldn’t do in this study.”
Study details
Real-world effectiveness of semaglutide and tirzepatide compared with bariatric surgery
Avery Brown, Suhani Patel, Akio Kozato, Karan Chhabra et al.
Published in Obesity on 25 June 2026
ABSTRACT
Objective
Directly compare the real-world effectiveness of semaglutide and tirzepatide to bariatric operations: sleeve gastrectomy and gastric bypass.
Methods
This study included adults with BMI ≥ 35 who received injectable semaglutide or tirzepatide (GLP-1RAs) or sleeve gastrectomy or gastric bypass (bariatric surgery) at two urban health systems from 2018 to 2024. Total weight loss (TWL) was compared up to 3 years post treatment with inverse probability weighting and mixed linear models. Intention-to-treat (any GLP-1RA) and per-protocol (1 year of continuous GLP-1RA orders) analyses were performed.
Results
Of 44,025 patients studied, bariatric surgery was associated with greater weight loss at 1, 2, and 3 years post treatment: semaglutide (n = 25,804) TWL (95% CI): 5.4% (5.3%–5.6%), 6.5% (6.4%–6.7%), and 7.4% (7.3%–7.6%); tirzepatide (n = 7308): 9.1% (8.9%–9.4%) and 10.8% (10.2%–11.3%); sleeve gastrectomy (n = 8728): 24.4% (24.3%–24.6%), 22.4% (22.3%–22.5%), and 22.0% (21.8%–22.1%); gastric bypass (n = 2185): 29.8% (29.7%–29.9%), 28.1% (28.0%–28.2%), and 28.4% (28.3%–28.5%). With 1 year of continuous GLP-1RA, findings were: semaglutide TWL: 7.2% (7.0%–7.4%), 8.0% (7.8%–8.2%), and 8.8% (8.6%–9.0%); tirzepatide TWL: 11.7% (11.4%–11.9%) and 11.9% (11.5%–12.3%).
Conclusions
In this retrospective two-centre study, bariatric surgery was associated with greater weight loss than GLP-1RAs among patients eligible for both options.
See more from MedicalBrief archives:
Bariatric surgery benefits confirmed in 10-year follow-up study
Weight-reduction surgery may prevent second heart attack and death
Weight-gain fears after stopping Ozempic unfounded – Cleveland Clinic study
Half of obese teens on Wegovy return to normal weight – STEP TEENS trial