A study found that surgery is more effective than drugs at reducing weight and diabetes measures in people with obesity and diabetes. Surgery was thought to be more necessary for low-income patients who cannot keep using expensive drugs or find it hard to follow a diet or exercise regularly, but in practice, surgery was highly effective for treating obesity and diabetes regardless of income level.
A research team led by Professor Mary Elizabeth Patti at the Joslin Diabetes Center at Harvard Medical School said on Jan. 20 that in a long-term randomized clinical trial conducted for more than 10 years in four U.S. cities, bariatric surgery was more effective than drugs or lifestyle changes at reducing weight and controlling blood sugar levels in people with type 2 diabetes, according to the international journal Annals of Internal Medicine.
◇ Surgery cuts body weight by more than 10% compared with drugs
Type 2 diabetes occurs when insulin is secreted but the body cannot use it properly, unlike type 1, in which the insulin hormone that controls blood sugar is not secreted at all. It mostly affects adults, and many patients have obesity or are overweight.
The researchers randomly assigned 355 people with type 2 diabetes in Boston, Cleveland, Pittsburgh and Seattle to receive nonsurgical treatment such as drugs or lifestyle changes between 2007 and 2013, or to undergo one of three types of bariatric surgery that reduce the size of the stomach.
Drugs included glucagon-like peptide (GLP)-1 injections such as Saxenda (liraglutide) from Denmark's Novo Nordisk and Mounjaro (tirzepatide) from Eli Lilly and Company. Bariatric surgery reduces weight by limiting nutrient intake through stomach size reduction. Methods include banding part of the stomach or removing a portion, but especially the Roux-en-Y gastric bypass, which cuts the upper stomach to create a pouch and connects this to the lower small intestine, is known to have a strong weight loss effect.
The researchers tracked 258 trial participants for up to 12 years after treatment or surgery, monitoring body weight and hemoglobin A1c (HbA1c), which reflects average blood sugar. Income level was compared using the Area Deprivation Index (ADI), based on residence zip codes. A higher ADI score indicates more severe economic and social hardship in that area.
The investigation found that regardless of ADI score, surgery reduced HbA1c more than drug therapy. Among the high-ADI group, the reduction from surgery was 1.29% greater than with drugs, and among the low-ADI group, it was 0.95% greater. The weight loss rate was also higher with surgery: 10.6% more than drugs in the high-ADI group and 13.3% more in the low-ADI group.
This aligns with earlier results that tracked 262 participants in the same trial in 2024. That investigation did not account for patients' income levels. Then, surgery produced a 28% weight loss, higher than the 10% with drug therapy. Blood sugar reductions were similar. In the nonsurgical group, HbA1c fell by 0.2 percentage points from 8.2%, while in the bariatric surgery group, it fell by 1.6 percentage points from 8.7%. Given that an HbA1c of 6.5% or higher indicates diabetes, surgery delivered a treatment effect close to cure.
◇ Even with potent anti-obesity drugs, alternative treatments are needed
The researchers said bariatric surgery does not treat obesity and diabetes simply by shrinking the stomach. Contrary to expectations, it also produces effects similar to those of GLP-1 drugs. GLP-1 is a hormone secreted from the small intestine after meals that promotes insulin secretion to lower blood sugar and suppresses glucagon, which raises blood sugar. Drugs that mimic this reduce appetite and increase satiety to lower weight. The team explained that bariatric surgery likewise reduces appetite.
After sleeve gastrectomy, ghrelin, a hormone that stimulates appetite, decreases early and remains low for up to five years. The researchers also said bariatric surgery changes how the gut interacts with nutrients, increasing GLP-1 hormone secretion.
But not many people undergo bariatric surgery because it permanently alters the digestive system. As anti-obesity drugs gain popularity, many think only low-income people who cannot afford drugs or do not have time to exercise are candidates for surgery. This long-term follow-up shows that surgery is more effective than drugs for treating obesity and diabetes regardless of income level.
Experts say that even if GLP-1 anti-obesity drugs are highly effective, various options should be considered to craft an optimal treatment strategy for each patient. Melanie Jay, a professor at New York University School of Medicine, said in a media interview, "Obesity requires lifelong management and there is no cure yet," and "it is very positive for patients to have access to a range of treatment approaches."
The researchers said people with severe obesity and diabetes, in particular, should consider surgery. Patti said, "Bariatric surgery led to better weight loss and blood sugar reduction than nonsurgical therapies across social backgrounds, yet it remains underused," and "especially if a person hopes to lose 100 pounds (about 45 kg), surgery is more effective than drugs."
References
Annals of Internal Medicine (2026), DOI: https://doi.org/10.7326/ANNALS-24-01882
JAMA (2024), DOI: https://doi.org/10.1001/jama.2024.0318