March 13, 2020

Weight loss lasts long after bariatric surgery


Diverse Kaiser Permanente patients maintained weight better after gastric bypass than after sleeve gastrectomy

SEATTLE, March 13, 2020People with severe obesity who had bariatric surgery maintained significantly more weight loss at 5 years than did those who did not have surgery. This is according to a large Kaiser Permanente study published March 13 in the Annals of Surgery: Weight Outcomes of Sleeve Gastrectomy and Gastric Bypass Compared to Non-Surgical Treatment. Although some weight regain was common after surgery, regain to within 5% of baseline was rare, especially in patients who had gastric bypass instead of sleeve gastrectomy.

“Earlier research has shown that bariatric surgery is the most effective weight-loss treatment for patients with severe obesity,” said first author David Arterburn, MD, MPH, a senior investigator at Kaiser Permanente Washington Health Research Institute (KPWHRI) and internal medicine physician at Washington Permanente Medical Group.

“Our new results could help ease concerns about long-term weight regain,” he added. “Along with safety worries and gaps in insurance coverage, such concerns have contributed to a low rate of bariatric surgery. Only about 1 in 100 eligible patients choose to have these procedures each year.”

Study findings

At 5 years after gastric bypass:

  • People had lost, on average, 22% of their initial body weight.
  • 25% had lost 30% or more of their total body weight.
  • Only 4% had regained weight to within 5% of their pre-surgical weight.

At 5 years after sleeve gastrectomy:

  • People had lost 16% of their body weight.
  • 8% had lost 30% or more of their total body weight.
  • About 10% had regained weight to within 5% of their pre-surgical weight.

At 10 years:

  • People who had gastric bypass maintained 20% weight loss, compared to 5% weight loss among those with usual medical care.
  • Longer-term results were not available for sleeve gastrectomy, because it is a newer procedure.

This weight-maintenance information is important because sleeve gastrectomy, which is simpler to perform than gastric bypass, now accounts for more than 2 in 3 bariatric surgery procedures. But earlier research from the same team showed that over 5 years follow-up, sleeve gastrectomy was associated with fewer re-operations and interventions to address problems or complications than was gastric bypass.

Monitor post-surgery weight regain

“It’s important to monitor patients closely for early signs of weight regain—and to intervene early with a detailed nutritional and medical evaluation to look for behavioral and surgical explanations for weight regain,” Dr. Arterburn said. People in the study who stopped losing weight early—within the first year, not the second—tended to have a greater risk of weight regain by 5 years.

This is one of a few large, long-term studies comparing the weight outcomes of bariatric procedures to non-surgical treatment:

  • It included more than 129,000 diverse patients at Kaiser Permanente in Washington and Northern and Southern California. More than 31,000 patients had bariatric surgery—more than 17,000 bypass and nearly 14,000 sleeve.
  • And nearly 88,000 control patients had similar characteristics but received usual medical care for their weight instead of bariatric surgery.

The study demonstrates the value of real-world evidence, because prior randomized trials did not find differences in weight loss between the two types of bariatric surgery. Differences between this and prior studies might be attributable to the characteristics of patients and surgeons involved in the studies.

Previously, the same research team showed that bariatric surgery was associated with half the risk of microvascular complications (nephropathy, neuropathy, and retinopathy) and of heart attacks and strokes compared to patients with type 2 diabetes and severe obesity undergoing usual medical care.

“Providers should engage all patients with severe obesity, especially those who also have type 2 diabetes, in a shared-decision-making conversation to discuss the benefits and risks of different bariatric procedures,” Dr. Arterburn said. “And more 10-year follow-up studies of bariatric surgery, particularly sleeve gastrectomy, are needed.”

Dr. Arterburn’s coauthors were Sebastien Haneuse, PhD, of Harvard T.H. Chan School of Public Health, Boston; Anita P. Courcoulas, MD, MPH, of University of Pittsburgh Medical Center, Pittsburgh, PA; Karen J. Coleman, PhD, of Kaiser Permanente Southern California, Pasadena; Lisa J. Herrinton, PhD, David Fisher, MD, Robert A. Li, MD, and Liyan Liu, MS, of Kaiser Permanente Northern California, Oakland; and Eric A. Johnson, MS, Mary Kay Theis, MS, and James R. Fraser of KPWHRI, Seattle.

The research was funded under a grant from National Institute for Diabetes and Digestive and Kidney Diseases (R01 DK105960).

A research brief sums up Kaiser Permanente research on obesity.

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 TwitterFacebook, 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:


Eric Johnson, MS

Senior Collaborative Biostatistician
Kaiser Permanente Washington Health Research Institute



Weight-loss surgery linked to fewer diabetes complications

Large, long-term study finds half as much nerve, kidney, and eye disease after bariatric surgery than with usual care.



Fewer heart attacks, strokes, and deaths after weight-loss surgery

Obese people with diabetes had fewer deaths in 5 years after bariatric surgery vs. usual care, in large, long-term study.



What motivates Dr. David Arterburn to study obesity?

He aims to reduce suffering from chronic illness. Plus, he's optimistic about research on body-weight regulation and on the psychology of weight-related behaviors.