Bariatric surgery is not only cost-effective for treating people who are severely obese, but also for those who are mildly obese, according to a new study from Washington University School of Medicine in St. Louis. The findings support making bariatric surgery available to all obese people, the researchers say.

Patients who have the surgery are more likely to keep weight off over time and have fewer medical problems related to their weight, indicating the procedure is a good value. But beyond being cost-effective, the analysis shows that bariatric surgery actually saves health-care dollars for the most severely obese patients who also have diseases related to their weight such as diabetes, heart disease and high blood pressure.

"If lifetime medical costs are taken into consideration, surgery saves severely obese patients money," says Su-Hsin Chang, PhD, a postdoctoral research associate in the Division of Public Health Sciences and first author on the study published in the journal Maturitas.

National Institutes of Health (NIH) guidelines say candidates for bariatric surgery should have a body mass index (BMI) of 40 or more (about 100 pounds overweight for men and 80 pounds overweight for women on average) or a BMI of 35 to 40 if they also have obesity-related diseases. Many insurance companies pay for the procedure only if patients meet these criteria.

"Insurance companies often pay for treating obesity-related diseases," Chang says. "But a portion of those costs could be saved if they paid for bariatric surgery for a wider range of obese patients."

Among the many strategies for treating obesity, including dieting, exercising and medications, only bariatric surgery has been shown to be effective in maintaining a healthy weight over the long term. But surgery also is the most expensive strategy. Cost estimates range from $20,000-$25,000 for the initial surgery and don't include follow-up care.

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In the United States, the upper limit for a medical procedure to be considered cost effective is $50,000 per quality-adjusted life year (QALY), a measure of the true value of treatment in terms of a person's quality and length of life. The assumption is that most people would be willing to pay up to $50,000 for an additional year of healthy life. Any amount less than that is considered cost effective.

Chang and her colleagues analyzed data from 170 studies looking at the effectiveness of bariatric surgery. The analysis only included studies that measured at least one outcome of interest such as weight loss, quality of life, complications and medical cost information.

They used this data to estimate and simulate the life expectancies and quality of life of people who underwent surgery versus people who did not. This simulation data then informed their cost-effectiveness analysis.

For the super obese, people with a body mass index (BMI) of 50 or greater (for example, a person who weighs 350 pounds and stands 5 feet 10 inches tall), the cost per quality-adjusted life year is actually negative. This means that, over a lifetime, the cost of bariatric surgery is less than the health-care costs associated with not having the procedure.

For the severely obese, people with BMIs of 40-50, the cost per QALY is about $1,900 for those with obesity-related disease and about $3,800 for those who are otherwise healthy. And for the moderately obese, people with BMIs of 35-40, the cost per QALY is about $2,400 for those with related medical problems and $3,900 for those who are healthy. While costs increase for healthier, less obese patients, all amounts are well below the $50,000 threshold.

"Other similar studies have found higher costs associated with bariatric surgery because they did not take the lifetime medical costs of the obesity-related diseases into consideration," Chang says.

This work also differs from previous cost analyses because it draws data from a much larger number of studies. While Chang says bariatric surgery in general is worth the high price tag, she points out that the analysis does not differentiate between types of bariatric surgery, such as lap band and gastric bypass.

"We did not intend to compare different types of weight loss surgery, but to generalize its effects and costs," she says. "Based on our analysis, bariatric surgery should be an option that is universally available to all obese people."

This work was supported by the Barnes-Jewish Hospital Foundation and the American Cancer Society Clinical Research Professorship.