Jury still out on bariatric surgery for patients with moderate obesity and diabetes

Bariatric surgery such as gastric bypass is associated with better short-term control of abnormal blood sugar and more weight loss than conventional nonsurgical therapy in diabetic patients who are moderately obese, but there is not enough evidence to more widely recommend the procedure, according to a new RAND Corporation study.

A review of more than 30 studies found that diabetic people with lost more weight and had better over two years if they were treated with bariatric rather than non-surgical alternatives like dieting and medications, according to a study published in the June 5 edition of the Journal of the American Medical Association.

However, the findings come from a relatively small number of trials performed at only a few academic surgery centers. More information is needed about how patients fare after two or more years, including complication rates and side effects, before the strategy can be more widely recommended, according to researchers.

"Bariatric surgery for diabetic people who are not severely obese has shown promising results in controlling glucose," said Dr. Melinda Maggard-, the study's lead author and a surgeon at the David Geffen School of Medicine at UCLA. "However, we need more information about the long-term benefits and risks before recommending bariatric surgery over non-surgical treatment for these individuals."

Bariatric surgery, which includes procedures such as gastric banding and gastric bypass, is now commonly used to produce weight loss and help manage related illnesses in people who are severely obese—generally people who are 100 pounds or more overweight.

To be classified as severely obese, a person must have a (a ratio of weight to height) of 40 or higher. A person who is 5 feet 10 inches and weighs 280 pounds has a of 40. People are deemed obese if their BMI is 30 or higher. Bariatric surgery is considered a for patients with diabetes and a BMI of 35 or for patients who have a BMI of 40 or more, regardless of whether they also have diabetes.

Bariatric surgery is being advocated as a treatment for diabetes in less-obese individuals, but there is no consensus about whether it's appropriate. In 2006, the federal Centers for Medicare & Medicaid Services would not approve coverage for patients with lower BMI and diabetes, whereas the U.S. Food and Drug Administration has approved gastric banding for individuals with a BMI of 30 to 35 who have an obesity-related illness.

The RAND study examined the evidence supporting the use of bariatric surgery to treat people who are at the low end of the obesity spectrum—those with a BMI of 30 to 35—and diabetes.

Researchers from the Southern California Evidence-Based Practice Center pooled together findings from other studies to assess the evidence, identifying 32 surgical studies, 11 systematic reviews on nonsurgical treatments and 11 large non-surgical studies that met criteria for the analysis.

Researchers found that bariatric surgery was associated with more short-term weight loss and better control of blood-sugar levels than nonsurgical therapy in patients with diabetes and a BMI of 30 to 35. Greater improvements were seen in patients undergoing gastric bypass than in those who received gastric banding.

However, much of the evidence came from studies with a small number of participants and where the surgeries were done by a single surgeon at one academic institution. Such studies may not represent results achieved in general clinical practice, according to researchers.

Before recommending weight-loss surgery for people on the lower end of the obesity spectrum, there needs to be additional and larger studies done to demonstrate the value of the approach, according to the study.

More information: JAMA. 2013;309(21):2250-2261

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