RAND Office of Media Relations
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April 4, 2005
Weight loss surgery helps severely obese people lose more weight than dieting and exercise alone, according to a RAND Corporation study issued today.
Severely obese people who undergo weight loss surgery typically lose about 45 to 65 pounds and maintain their lower weight for 10 years or longer, according to the study in the April 5 edition of the Annals of Internal Medicine.
The weight loss caused by surgery is accompanied by significant improvement in illnesses related to obesity such as diabetes, high blood pressure, sleep apnea and elevated cholesterol — even eliminating the problems in many patients, said Dr. Melinda Maggard, a UCLA surgeon and lead author of the study.
The study team — comprised primarily of researchers from RAND Health, the Greater Los Angeles VA Healthcare System and the David Geffen School of Medicine at UCLA — said its findings suggest that weight loss surgery also may provide benefits to people who are less severely overweight. But there is not yet enough evidence to conclude that surgery is superior to other weight loss methods for these patients.
In a related study in the same edition of the journal, the same study team reported that weight loss drugs promote moderate weight loss when prescribed along with recommendations for dieting and exercise among patients who are less severely overweight.
Patients who take prescription weight loss drugs lose an average of 10 pounds or less, with some evidence that people maintain the weight loss for at least a 6- to 12-month period, said Dr. Zhaoping Li, lead author of the diet drug study and director of clinical research at the UCLA Center for Human Nutrition. Patients in the diet drug study weighed less at the start of their treatment than those who underwent weight loss surgery.
“These studies should aid consumers by helping them make informed choices about weight loss treatment,” said Dr. Paul Shekelle of RAND and the Greater Los Angeles Veterans Affairs Healthcare System, who is the senior author of the two reports. “Surgery leads to more weight loss, but many of the surgeries are non-reversible. Drugs and dieting trigger less weight loss, but you can go off a drug if you don't like the side effects.”
To be classified as severely obese, a person must have a body mass index (a ratio of weight to height) of 40 or higher. A person who is 5 feet 10 inches and weighs 280 pounds has a BMI of 40. People are deemed obese if their BMI is 30 or higher.
Roughly one third of adults in the United States are obese, including about 9 million people who are severely obese. Only a small fraction of these people — about 140,000 — undergo weight-loss surgery each year.
WEIGHT LOSS SURGERY
Researchers from the Southern California Evidence-Based Practice Center examined the effectiveness and risks of weight loss surgery by analyzing nearly 150 published studies on the surgery, focusing on the most commonly performed procedures.
“This study presents the best evidence yet that weight loss surgery can be superior to other methods to help severely obese people lose weight,” Maggard said. “Weight loss surgery poses some risks and, for most procedures, will dramatically change the quantity and types of food patients will want to eat. But surgery, when combined with a healthy diet and regular exercise, can provide significant medical benefits to people who are severely obese.”
The study also found that:
- About 20 percent of the people who have weight-loss surgery experience complications. Although most are minor, some can be serious — such as intestinal leaks that can lead to another operation and prolonged hospitalization. The death rate from the procedures was less than 1 percent.
- Patients who undergo gastric bypass surgery — the most common form of weight loss surgery — typically lose about 20 pounds more than patients who undergo vertical-banded gastroplasty. Gastric bypass surgery involves decreasing the size of the stomach and making other intestinal changes to reduce the calories and nutrients the body can absorb. Vertical-banded gastroplasty uses a band and staples to reduce the stomach capacity, restricting the amount of food a person can consume.
- There was a significant learning curve among surgeons who perfomed the procedures. Complication rates and patients deaths were significantly higher among surgeons who had perfomed fewer than 50 of the surgeries.
WEIGHT LOSS DRUGS
The second study assessed the effectiveness of weight loss drugs by examining 78 studies of the most-popular prescription weight loss medications. It found that some drugs — particularly orlistat and sibutramine, the most widely used diet aids — promote moderate weight loss when prescribed along with recommendations for dieting.
“Medicines can be helpful as a part of a multi-pronged effort that also includes a healthy diet and exercise as a way to lose weight and keep the weight off,” Li said.
Most of the reports that researchers examined did not look at whether the drugs improve other medical problems. But the study did find evidence that people who lost weight using the drugs were less likely to develop diabetes, and weight loss has been associated with improved blood sugar and cholesterol levels.
Researchers found reports of side effects for each of the weight-loss drugs, including symptoms such as gastrointestinal upset and insomnia. But there was not enough information to determine whether the drugs may pose any long-term problems.
The thorough review of weight loss research found that very little research has been done on either surgery or medical treatment of obesity in children and adolescents.
The research was sponsored by the U.S. Agency for Healthcare Research and Quality.
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RAND Health is the nation's largest independent health policy research program, with a broad research portfolio that focuses on health care quality, costs, and delivery, among other topics.
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