Systematic reviews of medical literature between 2020 to 2024 show bariatric surgery, also known as metabolic or weight-loss surgery, produces the greatest and most sustained weight loss compared to GLP-1 receptor agonists and lifestyle interventions. The study was presented today at the American Society for Metabolic and Bariatric Surgery (ASMBS) 2024 Annual Scientific Meeting.

Researchers found lifestyle interventions such as diet and exercise resulted in an average weight loss of 7.4% but that weight was generally regained within 4.1 years. GLP-1s and metabolic and bariatric surgery proved far superior. Studies included thousands of patients from clinical studies and several randomized clinical trials.

Five months of weekly injections of GLP-1 semaglutide resulted in 10.6% weight loss and nine months of tirzepatide produced 21.1% weight loss. However, once treatment stopped, about half the lost weight returned within a year despite which drug was used. If injections were continued, tirzepatide patients plateaued at 22.5% weight loss at 17-18 months. Patients on semaglutide plateaued at 14.9% during the same time period.

Metabolic and bariatric surgery procedures gastric bypass and sleeve gastrectomy demonstrated total weight loss of 31.9% and 29.5% one year after surgery, respectively. Weight loss of approximately 25% was maintained for up to 10 years after surgery.

“Metabolic and bariatric surgery remains the most effective and durable treatment for severe obesity. Unfortunately, it also remains among the most underutilized,” said study co-author and bariatric surgeon Marina Kurian MD, NYU Langone Health. “Surgery needs to play a bigger role in obesity treatment and be considered earlier in the disease process. It is no longer a treatment of last resort and should not be withheld until more severe disease develops. There is no medical reason for this.”

The ASMBS reports that in 2022 nearly 280,000 metabolic and bariatric procedures were performed in the U.S., which represents only about 1% of those who meet eligibility requirements based on BMI. According to the U.S. Centers for Disease Control and Prevention (CDC), obesity effects 42.4% of Americans. Studies show the disease can weaken or impair the body’s immune system and cause chronic inflammation and increase the risk of many other diseases and conditions including cardiovascular disease, stroke, type 2 diabetes, and certain cancers. 

“While the new drug treatments show great promise and will lead to more people being successfully treated, particularly if prices come down and insurance coverage improves, we are barely using the best tool we have to fight obesity — metabolic and bariatric surgery, which is safer and more effective than ever before,” said Ann Rogers, MD, ASMBS President-elect and Professor of Surgery at Penn State College of Medicine, who was not involved in the study. “For many people, the risk of death from obesity, diabetes, and heart disease exceeds the risks of surgery.“

Study methodology

The study included a systematic review of studies that examined weight loss through lifestyle modification, GLP-1s (Semaglutide or tirzepatide) or metabolic and bariatric surgery. GLP-1 data included four randomized clinical trials conducted between 2021 and 2024 while conclusions on lifestyle modifications were based on a systematic review of eight studies. Metabolic and bariatric surgery (gastric bypass and sleeve gastrectomy) were subject to a review of 35 studies, including two randomized clinical trials. In all, researchers reviewed the weight-loss results of approximately 20,000 patients.