Weight loss surgery has long-term benefits for people with diabetes, study finds

By Mira Cheng, CNN

(CNN) — Bariatric surgery, also called weight loss surgery, leads to better blood sugar control and less medication use long-term in people with type 2 diabetes than non-surgical management with medications such as insulin and metformin, a new study found.

The study, published Tuesday in the journal JAMA, compared the blood sugar levels and medication regimens of 262 people who were randomly assigned to undergo weight loss surgery or non-surgical medical management, such as medication and lifestyle changes, for type 2 diabetes after seven to 12 years.

Participants who had weight loss surgery had significantly lower blood sugar levels and were on fewer diabetes medications than those who did not undergo surgery, the researchers, from University of Pittsburgh and other institutions, wrote. They were also more likely to achieve diabetes remission, which is defined as having non-diabetic blood sugar levels for at least three months without medication.

This research “provides the most robust evidence to date of the long-term efficacy of bariatric surgery for improving control of type 2 diabetes,” Dr. Thomas A. Wadden, a professor of psychology and former director of the Center for Weight and Eating Disorders at the Perelman School of Medicine at the University of Pennsylvania, wrote in an editorial that was published along with the research.

Weight loss surgery is a procedure in which the digestive tract is altered — typically, the size of the stomach is reduced — to help a person lose weight, according to the National Institute of Diabetes and Digestive and Kidney Diseases.

The resulting reduction in food intake and neurohormonal changes also lower blood sugar and thereby treat type 2 diabetes, Dr. Marilyn Tan, chief of the Endocrinology Clinic at Stanford Health Care, who was not involved with the research, wrote in an email to CNN.

“Though it’s a more invasive option than traditional diabetes medications and is a large commitment, it’s also an investment in long-term health,” Tan said.

Most health-care providers don’t currently recommend weight loss surgery for type 2 diabetes unless a person has a body mass index (BMI) of 35 or higher, and less than 1% of those people end up pursuing surgical treatment, according to the study.

However, Wadden said in an email to CNN that the new findings support the expanded use of bariatric surgery to those with a BMI less than 35 who have trouble controlling their blood sugar with medical management alone.

“I hope these results will encourage more insurers and payers to cover bariatric surgery for patients with type 2 diabetes and a BMI of 30 to 34.9,” he said. “It is a highly effective, long-term therapy for these individuals.”

Non-surgical medical management for type 2 diabetes involves lifestyle changes like reducing carbohydrate intake and increasing exercise, and using medications like metformin and occasionally insulin, Tan said. The goal is to lower hemoglobin A1c, the measure of average blood sugar levels over three months, below 7%.

“I’ve had multiple patients where despite hundreds of units of insulin a day, and despite their best efforts, they are unable to get their A1cs below 10%,” Tan said. “Then, after bariatric surgery, they can maintain A1c levels below the diabetes range without any medications. They also note that with the weight loss, they can be more active.”

Further research is needed to compare the clinical outcomes and cost efficacy of weight loss surgery and the new generation of anti-diabetes medications, such as Ozempic and Mounjaro, the editorial says.

The weight loss people have after surgery is key to improving diabetes outcomes as well as heart health, Tan said. Weight loss improves the body’s response to insulin, reduces inflammation and helps lower blood pressure and cholesterol. It can also improve arthritis so people can exercise more, she added.

The findings from this study also support the heart health benefits of weight loss surgery. People in the surgery group had significantly higher HDL or “good” cholesterol and lower triglycerides, a type of fat that can raise the risk of heart disease and stroke.

Despite the benefits, people are often hesitant to have weight loss surgery because it is invasive and comes with some risks, Tan said.

The study found that anemia (a lack of healthy red blood cells), bone fractures and gastrointestinal complications such as abdominal pain, nausea and vomiting were more common in people who had weight loss surgery.

These known complications result from nutritional deficiencies that can happen when the digestive tract is surgically altered. People who have surgery must change their diet and take vitamins regularly to avoid these problems, Tan said.

People who have the surgery can also gain back any weight lost, Tan added.

“Despite having the surgery, weight re-gain is possible if patients revert back to prior eating habits and quantities,” she said.

The study found that 51% of surgically treated participants achieved full remission of type 2 diabetes one year later, but only 18% maintained remission at seven years. This reduction in remission after surgery, which has been observed in previous research, is probably due to a combination of weight regain and the loss of insulin-producing cells over time, according to the editorial.

Even short-term diabetes remission has benefits in terms of reducing diabetes-related complications, such as eye, kidney and peripheral blood vessel disease, the editorial says.

Although bariatric surgery has a higher upfront cost than medical management — about $33,000 before insurance coverage — it is considered to be more cost-effective about five years after surgery, according to the editorial.

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