People who lose weight after stomach-shrinking surgery are typically able to keep the pounds off for two years or longer, suggests a new analysis of the evidence.
"There is no question there is some weight regain, but I think the durability of the results (in terms of weight loss) is pretty well expected and confirmed by this particular paper," said Dr. Nicolas Christou, a bariatric surgeon at McGill University in Montreal, Canada, who did not participate in the study.
Gastric bypass reduces the absorption of nutrients in food by shrinking the stomach and creating a detour around part of the small intestine.
A number of studies have shown the surgery is effective in helping people who are obese lose some of their excess weight.
"The question was always, what's it going to be like in the long term?" said Dr. Noel Williams, director of the Penn Metabolic and Bariatric Surgery Program at the University of Pennsylvania in Philadelphia, who worked on the study.
Williams and his colleagues gathered the results from 22 earlier trials that tracked more than 4,200 people for at least two years after they had gastric bypass surgery.
Patient follow-up ranged from two years to more than 12.
The researchers found people lost about two-thirds of their "excess weight" -- how many pounds overweight they were -- after surgery, and kept it off over time.
As an example, if a man weighs 350 pounds, but his healthy weight is 180, he is carrying 170 pounds of excess weight. Losing two-thirds of that extra weight would drop him down to 237 pounds.
Williams said a 65 to 75 per cent reduction in excess weight is considered an excellent result from surgery.
The findings, published in the Annals of Surgery, "provide support for the long term efficacy for gastric bypass," he told Reuters Health.
According to the American Society for Metabolic and Bariatric Surgery, about 220,000 people had weight loss surgery in 2009, with each procedure costing between $11,500 and $26,000.
To qualify for weight loss surgery, people typically need to have a body mass index -- a measure of weight in relation to height -- of at least 40, or between 35 and 40 if they also have an obesity-related illness.
That's the equivalent of a five-foot, six-inch person weighing at least 248 pounds or 217 pounds, respectively.
Weight loss is only one goal of the procedure, said Williams.
"What we also need to look at is improvement in comorbidities such as hypertension, diabetes (and) all these other problems in morbidly obese patients," he added.
Past studies have suggested weight loss surgery can lead to a smaller chance of heart attack and may cure diabetes in some cases (see Reuters Health reports of January 4, 2012 and June 23, 2011).
Williams said people will get the most out of their surgery if they are good about following up with visits to a weight loss clinic to help them maintain a healthy diet and lifestyle.