Weight loss lasts long after bariatric surgery, study finds

Weight loss was maintained better after gastric bypass than after sleeve gastrectomy in large study of diverse patients in Washington and California.

People with severe obesity who underwent bariatric surgery maintained significantly more weight loss at 5 years than those who did not have surgery according to a Kaiser Permanente study published March 16 in Annals of Surgery. 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.

Our new results could help ease concerns about long-term weight regain, which have contributed to a low rate of bariatric surgery -- only about 1 in 100 eligible patients choose to have these procedures each year."

David Arterburn, MD, MPH, first author, senior investigator at Kaiser Permanente Washington Health Research Institute and internal medicine physician at Kaiser Permanente in Washington.

The study found that:

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 initial 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. However, earlier research from the same team showed fewer reoperations and interventions to address problems or complications after sleeve gastrectomy than after gastric bypass, over a 5-year follow-up period.

"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 nonsurgical 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 loss 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 2 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."

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