WEIGHING THE OPTIONS
GLP-1 drugs vs. bariatric surgery for treating obesity
Prescriptions for the weight-loss drugs known as GLP-1s — especially semaglutide (Wegovy) and tirzepatide (Zepbound) — surged in recent years. Meanwhile, the number of weight-loss surgeries has declined. Known as bariatric surgery, these procedures remove or bypass part of the stomach. Many people in America meet the criteria for these proven obesity treatments.
"But obesity is a chronic, complex disease, so it may not be an either-or situation, as some people may benefit from a combined approach," says Dr. Eric Sheu, associate professor of surgery at Harvard Medical School and chief of bariatric and foregut surgery at Brigham and Women's Hospital.
Here's what you should know about how (and how well) both options work — not just for weight loss, but also for reducing your risk for serious health conditions linked to excess weight.
How GLP-1s work
GLP-1 stands for glucagon-like peptide-1, a naturally occurring gut hormone that helps control blood sugar and appetite. GLP-1 receptor agonist drugs (called GLP-1s for short) like semaglutide work by mimicking this hormone, increasing insulin release (which helps control diabetes), signaling to your brain that you're full and slowing digestion. Tirzepatide mimics GLP-1 and another hormone with similar effects called gastric inhibitory polypeptide, or GIP.
Most of the GLP-1s for weight loss are injected once weekly under the skin of your abdomen, thigh or upper arm, using a penlike device with a needle the width of a human hair. In studies, people lost 15% to 20% of their body weight, on average.
Pros and cons of GLP-1s
"GLP-1 medications are great, and there are similar promising drugs in the pipeline," Sheu says.
Future drugs may be easier to take and have fewer side effects. For example, a pill form of semaglutide for weight loss (called the Wegovy pill) became available in early January 2026.
GLP-1s can produce side effects such as nausea, vomiting and diarrhea.
"And their real-world effectiveness is about half of what's been reported in the clinical trials, probably because most people stop taking them, often for a combination of reasons including side effects, cost and access," Sheu says.
To maintain your weight loss, you have to take the drugs for the rest of your life, which many people don't realize, he adds.
Initially, the average cost ranged near $1,000 per month, but prices are in flux and recently dropped. Insurance coverage varies widely but is less common for people without related health conditions.
Gastric sleeve
This surgery removes about 80% of the stomach, leaving a banana-shaped tube. It's less invasive than gastric bypass because the small intestine is not cut.
Gastric bypass
Gastric bypass converts the upper stomach into an egg-sized pouch and reroutes the small intestine to the pouch.
How bariatric surgeries work
The two most common types of bariatric surgery are sleeve gastrectomy and gastric bypass. Both approaches are minimally invasive, meaning they involve very small incisions and usually require just one night in the hospital.
Both surgeries reduce the size of the stomach, but more importantly alter your body's secretion of the gut hormones that regulate hunger and metabolism, Sheu says.
"For example, the surgeries increase GLP-1 and GIP levels in the body, which is a key reason they trigger weight loss," he says.
In addition, diabetic control improves within days of the surgery.
Weight-loss drugs under development aim to mimic other gut hormones that change after bariatric surgery, he adds.
Gastric bypass leads to the greatest weight loss (about 33%) and shows the greatest success for resolving diabetes.
But sleeve gastrectomy is a simpler, shorter procedure. It accounts for about 70% of all bariatric surgeries and leads to an average weight loss of about 25%.
Pros and cons of bariatric surgery
A 2025 study in Nature Medicine that compared GLP-1 drugs to bariatric surgery found that people who had surgery lost more weight and had far fewer serious health problems — including heart attacks, strokes, kidney disease and diabetes-related eye damage — during the follow-up period, which lasted a median of nearly six years. However, more than half of the people using GLP-1s took earlier, less effective versions.
For people with both obesity and diabetes, surgery is clearly more effective for preventing deaths from cardiovascular disease, Sheu says. That benefit far outweighs risks associated with surgery, which has a complication rate lower than hip replacement surgery. And studies show most people maintain their weight loss for up to a decade.
Surgery costs between $17,000 and $26,000 and is typically covered by insurance. But the procedures require several weeks of recovery, are irreversible (with rare exceptions) and require lifelong dietary changes.
A combo approach?
These days, most people who consider bariatric surgery have already tried GLP-1 drugs without success, Sheu says.
After bariatric surgery, the resulting hormone changes persist to different degrees. "A year or two after surgery, some people regain their hunger response and put on weight," Sheu says.
For them, GLP-1s can be a good option to help maintain their weight loss. "The two therapies may work best in combination, but we're still trying to figure out the best sequence and timing," he adds.
Who qualifies?
GLP-1s usually are prescribed only for people with a body mass index (BMI) of at least 30 — or at least 27 for people with one or more of these weight-related medical conditions:
■ Diabetes
■ High blood pressure
■ Elevated cholesterol
■ Obstructive sleep apnea
■ Cardiovascular disease
For bariatric surgery, the BMI cutoff used to be at least 40 (or at least 35 with a weight-related condition). In recent years, obesity and diabetes organizations have advocated for lowering the cutoffs to 35 and 30, respectively. Some insurers now cover bariatric surgery for people at those lower thresholds.
You can calculate your BMI at the website of the National Institutes of Health (nhlbi.nih.gov/ calculate-your-bmi).
