Gastric bypass surgery is best for weight loss for severe obesity

Largest long-term national study of bariatric surgery, comparing 3 most common operations, is among first PCORnet® results

SEATTLE, October 29, 2018 — 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: “Comparative Effectiveness of Bariatric Procedures for Weight Loss and Safety,” with an accompanying editorial.

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 U.S. 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.

What about sleeve?

“Bariatric surgery is widely considered the most effective way to treat severe obesity and induce long-term weight loss,” said first author David Arterburn, MD, MPH, an internist and senior investigator at Kaiser Permanente Washington Health Research Institute. “We wondered about sleeve gastrectomy, which is easier to perform than bypass and has quickly become the most commonly performed bariatric procedure in the United States. Because it’s the newest—introduced less than a decade ago—less evidence has been available to compare it against the longstanding gastric bypass and adjustable gastric band.”

The investigators found that:

• People who had gastric bypass surgery had lost 31 percent of their weight at the first year and maintained 26 percent of their loss at 5 years. 
• People who had sleeve gastrectomy had lost 25 percent of their pre-surgery body weight at 1 year and maintained 19 percent weight loss at 5 years.
• 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.
• By contrast, adjustable gastric banding was much less effective for losing weight and keeping it off, with 14 percent and 12 percent of weight lost at 1 and 5 years, 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 sleeve are effective for lasting weight loss for adults with severe obesity,” said Kathleen M. McTigue, MD, MPH, MS, 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 health care providers about the respective benefits and risks of the most common weight-loss procedures.”

Members of the same PCORnet® Bariatric Study Collaborative team had found similar results in teenagers.

Subgroups and short-term safety

Because of the large sample size, the researchers could examine subgroups of people to assess whether certain characteristics improved or worsened their chance of weight loss success. They found that men, African-Americans, Hispanics, people age 65 and older, and people with diabetes or lower BMIs (less than 50) tended to lose less weight than did other people in the study. But these differences between patient groups were small—less than 3 percent differences in weight lost at 1, 3, and 5 years across groups—which was much less than the differences between the procedures. For instance, the difference between weight lost with gastric bypass and sleeve gastrectomy was 6 percent at 1 year and 7 percent at 5 years.

The 30-day risk of major adverse events, such as a prolonged hospitalization or another operation, were generally low across all three procedures. Sleeve gastrectomy had the lowest rate of major adverse events (2.6 percent), followed by gastric banding (2.9 percent), and then gastric bypass (5.0 percent).

The new results are among the first to be produced using the resources of PCORnet®, an innovative initiative funded by the Patient-Centered Outcomes Research Institute (or PCORI). PCORnet® is designed to produce clinical insights faster and less expensively than traditional clinical studies. It involves multiple individual networks that together represent more than 100 million patients.

The network securely collects health information during routine care—not including data that could help identify individuals—to produce real-world evidence with outcomes that matter to patients, who are full partners in this research.

Input from patient stakeholders

“Our patients and providers were critical to the success of this study,” said Karen J. Coleman, PhD, MS, another study leader and a research scientist at Kaiser Permanente in Southern California’s Department of Research & Evaluation in Pasadena. “They helped us craft the question, pick the variables to study, interpret the findings, and present the results. We could never have done such a comprehensive study without their partnership.”

“We helped the group think through the most important questions for patients, like risks and safety concerns,” said the Rev. Neely Williams, MDiv, a patient-principal investigator on the study and the CEO of the Community Partners’ Network in Nashville. “We also explored how best to share evidence with patients.”

The PCORnet® Bariatric Study Collaborative team is continuing to examine the outcomes of different types of weight-loss surgery for longer-term safety as well as outcomes in people with diabetes.

This PCORnet® study, registered at ClinicalTrials.gov (NCT02741674), was funded by PCORI through PCORI Award OBS-1505-30683.

For the PCORnet® Bariatric Study Collaborative, the other coauthors are Robert Wellman, MS, R. Yates Coley, PhD, Andrea J. Cook, PhD, Jane Anau, and Roy Pardee, JD, MA, of Kaiser Permanente Washington Health Research Institute; Sameer Murali, MD, of Kaiser Permanente in Southern California’s Department of Research and Evaluation in Pasadena; Sengwee Toh, ScD, Jessica Sturtevant, MS, and Casie Horgan, MPH, of Harvard Medical School’s Department of Population Medicine and Harvard Pilgrim Health Care Institute in Boston; Ana Emiliano, M.D., of Rockefeller University in New York; Steven R. Smith, MD, of Florida Hospital’s The Translational Research Institute for Metabolism and Diabetes in Orlando; Andrew O. Odegaard, PhD, MPH, of the University of California, Irvine School of Medicine’s Department of Epidemiology; Cheri Janning RN, BSN, MS, of Duke Clinical & Translational Science Institute in Durham, NC; Anita Courcoulas, MD, MPH, of the University of Pittsburgh’s Department of Surgery.

About Kaiser Permanente Washington Health Research Institute

Kaiser Permanente Washington Health Research Institute (KPWHRI) improves the health and health care of Kaiser Permanente members and the public. The institute has conducted nonproprietary public-interest research on preventing, diagnosing, and treating major health problems since 1983. Government and private research grants provide our main funding. Follow KPWHRI research on Twitter, Facebook, and LinkedIn, or subscribe to our free monthly newsletter. 

About Kaiser Permanente

Kaiser Permanente is committed to helping shape the future of health care. We are recognized as one of America’s leading health care providers and not-for-profit health plans. Founded in 1945, Kaiser Permanente has a mission to provide high-quality, affordable health care services and to improve the health of our members and the communities we serve. We currently serve more than 12.4 million members in eight states and the District of Columbia. Care for members and patients is focused on their total health and guided by their personal Permanente Medical Group physicians, specialists and team of caregivers. Our expert and caring medical teams are empowered and supported by industry-leading technology advances and tools for health promotion, disease prevention, state-of-the-art care delivery and world-class chronic disease management. Kaiser Permanente is dedicated to care innovations, clinical research, health education and the support of community health. For more information, go to: kp.org/share.