NEW YORK (Reuters Health) – More than 20 years of evidence suggests that bariatric surgery produces greater weight loss and more type 2 diabetes remissions than nonsurgical treatments for the obese, according to a review.
The results, from a National Institutes of Health (NIH) symposium held last year, support the idea that weight loss surgeries are effective and safe, at least within the first two to five years after surgery. But more studies of long term effects are needed, the authors say.
The NIH last held a consensus panel on the issue in 1991. Since then, bariatric surgeries have become much more routine and more small clinical trials and large observational studies on the outcomes of surgery have been done.
In a new clinical review in JAMA Surgery, experts from the National Institute of Diabetes and Digestive and Kidney Diseases and the National Heart, Lung, and Blood Institute at the NIH in Bethesda, Maryland, as well as the Group Health Cooperative in Seattle and the University of Pittsburgh Medical Center summarize the evidence since 1991.
Several small trials have found greater weight loss and type 2 diabetes remission after bariatric surgeries compared to nonsurgical methods like dieting and behavioral therapies, they write.
Most bariatric surgeries are only approved for patients who have failed to lose significant weight with diet and exercise.
People who get the surgery tend to lose around 20 to 30 percent of their body weight in the following years, compared to little or no weight loss for similar people who do not get the surgery, according to recent long-term studies.
But there are still gaps in bariatric surgery research, the authors point out.
More studies are needed to determine how long type 2 diabetes remission lasts, to assess how often complications occur from surgery and what predicts those complications, and to measure long-term health outcomes, they write.
Common complications include hypoglycemia, nausea or vomiting and insufficient weight loss, according to the authors.
There should also be more research into optimal dietary and nutritional management following bariatric procedures, as well as how to manage specific complications of bariatric operations.
In 1991, the consensus panel concluded that Roux-en-Y gastric bypass and vertical banded gastroplasty procedures were safe and effective for people with a body mass index (BMI) of 40 or more, or with a BMI of 35 or more in addition to serious medical problems like diabetes, coronary heart disease, sleep apnea, high blood pressure or severe arthritis.
Whether or not it was meant as such, that consensus became “gospel” for doctors, hospitals and insurers, who to this day rarely agree to cover the surgery for people who do not meet those criteria, said Dr. Justin B. Dimick, chief of minimally invasive surgery at the University of Michigan in Ann Arbor.
“The evidence base then was pretty weak,” he said. “Now we have much more evidence, but it’s not being brought to bear on decision making.”
Studies now suggest that bariatric surgery may be the best option for reversing type 2 diabetes for people with a BMI as low as 30, but the new consensus panel did not revise their 1991 guideline in this regard, he said.
“The relationship between BMI and mortality is not as strong as we thought it was, but between type 2 diabetes and death, it is,” Dimick said. “A lot of people with a BMI of 40 are fairly healthy, but others are at a BMI of 33 and have type 2 diabetes and are at greater risk.”
Dimick was not involved in the new review, but coauthored an accompanying editorial in JAMA.
Today, lap band surgery, in which an adjustable device is placed over the top portion of the stomach, has dropped off in popularity due to long-term complications, erosion and poor weight-loss results, Dimick said.
The most common option now is gastric sleeve surgery, in which much of the stomach is removed and the remainder is stapled into a small sleeve. The gastric sleeve procedure itself carries more risks but has had fewer long-term complications, Dimick said.
The authors do state that bariatric surgical techniques and their short-term outcomes have improved greatly since 1991.
“In general what we have learned in the last five years is it is very safe and extraordinarily effective when you compare it to nonsurgical options like diet and behavioral therapy,” Dimick told Reuters Health.