BATON ROUGE, LA -- As obesity rates have increased, gastric bypass and other abdominal surgeries have gained in popularity. Despite other reports that extreme weight loss reduces lifespan, new research suggests that these surgeries may be extending or saving lives.

An international research team tracked more than 4,000 obese individuals for 11 years. About half of the individuals underwent bariatric surgery. The other half received conventional treatments. Researchers found that bariatric surgery for severe obesity appears to be associated with long-term weight loss and decreased overall mortality.

The research is the first major report to confirm that weight loss in excess of 50 pounds decreases mortality. Some past studies found that weight loss was associated with increased mortality.

“This was an interventional study, meaning we enrolled obese patients into the study who had sought surgery and compared them to a similar group who were undergoing conventional treatment during the same time frame,” says researcher Claude Bouchard of the Pennington Biomedical Research Center. “Previous studies were based on much smaller sample sizes with shorter follow-up periods and did not have the proper control group for comparison. What we learned is that an often controversial method—surgery—presents clear clinical evidence of being beneficial.”

One scientific limitation is that ethically, it is not possible to randomly assign subjects into a surgery group or a non-surgery group, Bouchard says. This study compared individuals who had made their treatment decisions individually, so the study examined self-selected groups rather than randomized groups, a situation that is not likely to change in studies of this type, he says.

The average 11-year weight loss of the non-surgery group was less than 2 percent, while the average weight loss among the three surgical groups ranged from 14 to 25 percent. During the study, researchers recorded 129 deaths in the non-surgery group and 101 in the surgery group, most commonly caused by myocardial infarction and cancer. This result indicates a 23 percent reduction in total mortality within the surgical groups.

“We count these results as a milestone in our understanding of the benefits of bariatric surgery for obesity,” Bouchard says. “We are confident in the results and believe this will lead to an acceptance that bariatric surgery is a viable, life-saving option for severely obese patients.”

All results were published in the The New England Journal of Medicine.