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Metabolic and bariatric surgery is more effective for long-term weight loss than lifestyle changes and GLP-1 medications like Ozempic, Wegovy, and Zepbound. Nastasic/Getty Images
  • New research found that metabolic and bariatric surgery resulted in greater weight loss compared to two GLP-1 drugs and lifestyle modifications.
  • Bariatric surgery is a one-time procedure, while people need to continue receiving weekly injections of GLP-1 drugs to maintain most of the weight loss.
  • Doctors continue to use all three types of treatments, depending on a patient’s specific situation.

Metabolic and bariatric surgery led to greater weight loss compared to two newer anti-obesity drugs and lifestyle modifications, and it also provided long lasting results, new research shows.

In this preliminary study, researchers reviewed earlier studies looking at the benefits of these types of treatments for weight loss.

They found that lifestyle modifications such as diet and exercise resulted in an average weight loss of 7.4%. People generally regained this weight in about 4 years.

In contrast, people lost more weight with GLP-1 receptor agonists or metabolic and bariatric surgery, and they kept the weight off longer — with surgery providing the best results.

“Metabolic and bariatric surgery remains the most effective and durable treatment for severe obesity,” study co-author Marina Kurian MD, a bariatric surgeon at NYU Langone Health, who was also one of the study’s authors, said in a release. “Unfortunately, it also remains among the most underutilized.”

The study was presented on June 11 at the American Society for Metabolic and Bariatric Surgery (ASMBS) 2024 Annual Scientific Meeting. The results have not been published yet in a peer-reviewed journal.

In the study, researchers conducted a systematic review of studies that examined weight loss through the use of GLP-1 medications semaglutide (Ozempic, Wegovy) or tirzepatide (Mounjaro, Zepbound), lifestyle modifications, or metabolic and bariatric surgery (gastric bypass or sleeve gastrectomy).

This included four randomized clinical trials looking at the benefits of GLP-1 drugs, eight studies on lifestyle modifications, and 35 studies on metabolic and bariatric surgery, including two randomized clinical trials on surgery. These studies involved about 20,000 patients.

After 20 weeks of weekly injections of GLP-1 receptor agonist semaglutide, people lost, on average, 10.6% of their weight. After 36 weeks of weekly injections of tirzepatide, another GLP-1 drug, people lost an average of 21.1% of their weight.

Tirzepatide also targets another hormone, GIP, making it a dual-acting drug.

People who stopped receiving weekly injections of semaglutide or tirzepatide regained about half the lost weight within a year, researchers found.

Those who continued receiving semaglutide injections plateaued after 17 to 18 months at a weight loss of 14.9%. Those who continued with tirzepatide plateaued at 22.5% weight loss over that same period.

Dr. Jaime Almandoz, associate professor in UT Southwestern Medical Center’s Department of Internal Medicine, Division of Endocrinology, who was not involved in the study, said it is not surprising that people regained some weight after they stopped taking the anti-obesity medications.

“Obesity is a chronic and complex disease. Like most medical therapies for chronic diseases like hypertension and elevated cholesterol, if you discontinue effective treatments, the patient experiences disease recurrence,” he told Healthline.

Researchers also found that metabolic and bariatric surgery procedures — gastric bypass and sleeve gastrectomy — led to an average weight loss of 29.5% to 31.9% one year after surgery. People maintained a weight loss of about 25% for up to 10 years after surgery.

“Bariatric surgery induces more of a long-term metabolic change than the [GLP-1] drugs can because the drugs leave your system within a week,” said Dr. Mir Ali, MD, bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center in Fountain Valley, Calif, who was not involved in the study.

In addition, “even people who’ve regained some weight [after bariatric surgery] still have some of the protective effects against diabetes and other conditions due to metabolic changes,” he told Healthline.

Almandoz emphasized that metabolic and bariatric surgery and GLP-1 drugs do not cure obesity.

People can regain weight due to a variety of factors, he said, such as “metabolic adaptation to weight loss, which is where there are neurohormonal changes in the body that make us require fewer calories than would be predicted for our age, sex, and body composition.”

Although metabolic and bariatric surgery are effective treatments for obesity, not everyone qualifies for these procedures. People who are good candidates include those with a body mass index (BMI) of 40 or more, those with a BMI of 35 or more and a serious obesity-related health problem such as type 2 diabetes, heart disease, or sleep apnea.

In 2022, nearly 280,000 people had metabolic and bariatric surgery, according to the ASMBS. This, said Ali, represents only 1% to 2% of people who are eligible for one of these procedures.

“There are multiple factors for that,” he said, “obviously access to insurance, but also some misinformation about the safety of the surgery.”

People may have heard that metabolic and bariatric surgery is dangerous, Ali said, but it’s actually very safe and is safer than gallbladder surgery.

Almandoz said anti-obesity medications are similarly underutilized for treating obesity, in part due to insurance coverage, affordability, and access — which are also issues with metabolic and bariatric surgery.

“This is unfortunate, as both medications and surgery are safe and effective tools for treating obesity,” he said. “Many of the newer, highly effective medications used to treat obesity are also used for treating type 2 diabetes.”

GLP-1 drugs have also been shown to reduce the risk of:

Metabolic and bariatric surgery have similar benefits for treating type 2 diabetes, liver disease, and cardiovascular disease.

Although metabolic and bariatric surgery led to greater weight loss in this study, the best approach still depends upon a person’s unique situation.

“In selecting treatments for this chronic, complex disease, we need to create a patient-centered approach that targets overall improvements in health and quality of life and not just weight loss,” said Almandoz.

“We also need to respect patient autonomy, as there is a growing trend for people to prefer anti-obesity medications over bariatric surgery,” he said.

Ali said that sometimes, these treatments are used alongside each other. For example, “we encourage people to lose weight before surgery with diet,” he said, “and that really gets things jump-started.”

“Also, when we have patients who are struggling after surgery to lose that last bit of weight, we can help them with medications,” he said. “So we do combine modalities. It just depends on the patient’s situation.”

Researchers reviewed previous studies looking at the weight loss benefits of metabolic and bariatric surgery (gastric bypass and sleeve gastrectomy), lifestyle modifications, or GLP-1 receptor agonist drugs (semaglutide and tirzepatide).

Bariatric surgery provided greater weight loss compared to the other types of treatment, with long-lasting benefits. Bariatric surgery is a one-time treatment, while people need to keep receiving GLP-1 drugs to maintain the weight loss.

Doctors may recommend more than one type of treatment for obesity. For example, they may advise patients to lose weight with diet and exercise before undergoing metabolic and bariatric surgery. Or they may prescribe GLP-1 drugs after surgery to help patients lose weight.