Adults with severe obesity had greater initial and sustained weight loss with gastric bypass surgery than either sleeve gastrectomy or adjustable gastric banding, according to a new study published today in the Annals of Internal Medicine.

This is the largest long-term study of bariatric surgery to date. It included more than 46,000 patients at 41 participating health systems in 11 Clinical Data Research Networks nationwide, thanks to its use of a large new resource called PCORnet, the National Patient-Centered Clinical Research Network.

Bariatric surgeons can use various operations to help people lose weight by making changes to their digestive system. This study did a head-to-head comparison of 1-, 3- and 5-year results from the three most commonly performed weight-loss operations: gastric bypass, sleeve gastrectomy, and adjustable gastric banding.

The findings are important because severe obesity-a body mass index (or BMI) of at least 35 kg / m2 -affects more than 15 percent of US adults, according to the National Health and Nutrition Examination Survey.

National Institutes of Health guidelines consider people with a BMI of 40 kg / m2, or at least 35 kg / m2 for people with diabetes or other obesity-related diseases, eligible for  bariatric surgery .

"Bariatric surgery is considered the most effective way to treat severe obesity and induces long-term weight loss," said David Arterburn, MD, an internist and senior investigator at the Kaiser Permanente Washington Health Research Institute.

"We wondered about the sleeve gastrectomy, which has become the most commonly performed bariatric procedure in the United States. Because it's the newest-less than a decade ago-less evidence has been available to compare it against the longstanding gastric bypass and adjustable gastric band," said Arterburn.

The investigators found that:

1. People who had  gastric bypass surgery  had lost 31% of their weight at the first year and maintained 26% of their loss at5 years

2. People who had sleeve gastrectomy had lost 25 percent of their pre-surgery body weight at one year and maintained 19% weight loss at 5 years

3. That translates into a 19-pound difference in weight loss between gastric bypass and sleeve gastrectomy at 5 years for the average person in this study, who weighed 277 pounds before surgery.

4. By contrast, adjustable gastric banding was much less effective for losing weight and keeping it off, with 14 percent and 12 percent of weight loss at 1 and 5years, respectively. Gastric banding used to be the most commonly performed bariatric procedure, but it now represents just 10 percent of bariatric procedures.

"These findings give strong evidence that bypass and weight loss for adults with severe obesity," said Kathleen M. McTigue, MD, another study leader and an associate professor of medicine and epidemiology at the University of Pittsburgh.

"We hope this helps people to make more informed decisions about their care, as they talk with their healthcare providers about the respective benefits and risks of the most common weight-loss procedures," said McTigue.