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.
Some complications from surgery did occur, such as pulmonary embolism and post-operative death. Most studies had no deaths and those that did had one or two.
Although they aimed to update the review with information about bariatric surgery in patients younger than 18 years, researchers found no studies that compared surgery with conventional management in this group of patients, so they could not comment, Colquitt said. They also excluded older trials that examined surgical techniques no longer used "to keep the review as relevant and helpful as possible," Colquitt said.
"The frontline question is, 'Is surgery better for patients with lower levels of obesity?' Those are areas of research that are just beginning to come to light," Hallowell said.
"Their findings are very important. In the small number of randomized controlled trials to look at, there's clear evidence that surgery is better than not having surgery," Hallowell said.
"There are risks to surgery - we don't want to minimize that to any degree - but the health benefits noted in these studies certainly outweigh the risks for patients who undergo it," Hallowell said.
This project received funding from the UK's National Institute for Health Research (NIHR) Health Technology Assessment Programme.
The Cochrane Collaboration is an international nonprofit, independent organization that produces and disseminates systematic reviews of health care interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. Visit http://www.cochrane.org for more information.
Colquitt JL, et al. Surgery for obesity. The Cochrane Database of Systematic Reviews 2009, Issue 2.