Surgeons once recommended weight-loss surgery only for severely obese patients who failed to drop pounds with conventional weight-loss methods, but a review now finds that bariatric surgery helps the moderately obese lose more weight, too.
"Until recently, only people with severe obesity - with a body mass index (BMI) greater than 40 - were considered for bariatric surgery," said review author Jill Colquitt, Ph.D.
But studies, such as those included in this review, now examine the effects of surgery on people with a BMI of 30 to 40 who have diseases such as type 2 diabetes or hypertension that potentially could improve, said Colquitt, a senior research fellow at the University of Southampton, in England.
"We see a wide range of patients who consider surgery. The majority are people that attempted medical weight loss for years and decades without success, and they have an intimate understanding of what morbid obesity means to them in their life. They're looking for a therapy that can give them some help," said Peter Hallowell, M.D., an assistant professor of surgery at the University of Virginia. He has no affiliation with the review.
In the new review - the third update of a 2002 review - researchers led by Colquitt examined 26 previously published studies on bariatric surgery involving 5,766 patients. Five of the included trials took place in the United States.
Six studies compared bariatric surgery outcomes to those from conventional weight loss management. Twenty studies compared different bariatric surgery procedures.
The review appears in the latest issue of The Cochrane Library , a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews like this one draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.
The conclusions of the new review were broadly similar to previous research, Colquitt said. Researchers found that weight reduction surgery in obese patients led to more weight loss than conventional methods, such as dieting and exercise.
However, "since we conducted the first review, we made changes to the inclusion criteria to include people with a lower threshold of obesity," Colquitt said.
Specifically, two trials examined people of moderate obesity - with BMIs between 30 and 40 - who had weight-related conditions such as type 2 diabetes.
In these patients, weight reduction was greater two years after surgery and conditions like diabetes and metabolic syndrome improved, compared to those in the conventional management group.
For example, one study found that moderately obese people who received weight-loss surgery dropped 87.2 percent of excess weight. In comparison, those who used drugs, diet and exercise only lost 21.8 percent of excess weight.
The review evidence also suggested that the type of surgery a patient had affected their weight-loss results. In gastric bypass, surgeons make the stomach smaller and shorten the length of the small intestine, whereas gastric banding involves using silicone bands that the physician can adjust to reduce the stomach's size.
Researchers found that gastric bypass led to greater weight loss than vertical banded gastroplasty or adjustable gastric banding. The results were similar for gastric bypass and two techniques called isolated sleeve gastrectomy and banded gastric bypass.
However, it is not possible to draw any conclusions because of the small number of studies comparing each procedure and the risk of bias in some of the trials, Colquitt said.