The greatest research need regarding bariatric surgery is the critical lack of information about long-term durability and complications of the procedures, according to a report published online Nov. 4 in JAMA Surgery.

Bariatric surgery “results in greater weight loss than nonsurgical treatment,” but that crucial information about long-term outcomes – “at least 10 years’ worth” – is still missing, said Dr. Bruce M. Wolfe of Oregon Health and Science University, Portland, and Steven H. Belle, Ph.D., of the epidemiology department, University of Pittsburgh. They were speaking at a symposium sponsored by the National Institute of Digestive and Kidney Diseases and the National Heart, Lung, and Blood Institute to review the best available evidence on bariatric surgery outcomes from the most recent large observational studies and randomized clinical trials.

Very large multicenter, randomized, controlled trials are the best type of study to provide this information but are prohibitively expensive, especially given the difficulty retaining participants in weight-loss studies. Any such trial would require very large numbers of treatment centers and patients to generate results that were adequately powered and generalizable, they wrote (JAMA Surg. 2014 Nov. 4 [doi: 10.1001/jamasurg.2014.2440]).

Future research must address the substantial variability in weight loss after bariatric surgery, as well as the equally substantial variability in its effect on diabetes, hypertension, dyslipidemia, obstructive sleep apnea, and psychological and psychosocial issues. And long-term gastrointestinal complications must be a specific focus because these procedures alter the GI anatomy, and adverse effects may take many years to manifest.

“In summary, bariatric surgery offers the potential to address the morbidity and mortality of the obesity epidemic, but important research questions remain unresolved,” according to Dr. Wolfe and Dr. Belle.

The symposium was convened by the National Institute of Diabetes and Digestive and Kidney Diseases and the National Heart, Lung, and Blood Institute’s division of cardiovascular sciences. Dr. Wolfe reported serving as a research consultant to EnteroMedics.