A graded, evidence-based summary of evidence for bariatric surgery

Obesity is a growing epidemic in the United States, with more than 60% of the population currently classified as overweight or obese [1]. One form of treatment for obesity-bariatric surgery-is the focus of this summary of evidence. Questions for evaluation of evidence regarding the subject of bariatric surgery and its relationship to Medicare beneficiaries focus on types of surgery and their outcomes in persons that have at least 1 preoperative comorbidity compared with no preoperative comorbidities. Overweight people are classified into 4 groups based on body mass index (BMI): overweight, 25 to 29.9 kg/m²; class I obesity, 30 to 34.9; class II obesity, 35 to 39.9; and class III (extreme) obesity, ≥ 40. By these definitions, approximately 27% of the U.S. population is obese and an additional 34% are overweight [1]. Obesity is more common in women; overweight is more common in men. Obesity is especially common in African-Americans, Native Americans, native Hawaiians, and some Hispanic populations [2]. Data for the extent of obesity in the Medicare population indicate that in 1999-2000, 33% of men and 39% of women age 65 to 74, and 20% of men and 25% of women over age 74, were obese. In 2004, Livingston [3] used the 2000 National Health Interview Survey (NHIS) database to estimate the number of persons with obesity eligible for surgery, using the standard definition of morbid obesity, to be more than 5 million persons (2.8% of the U.S. population). Of that number, 4.6 million have class III obesity and 9 million are in the class II range. In a recent article, Buchwald et al. [4] estimated the current figure as 5%. The Massachusetts technology assessment (TA) reported that weight loss in bariatric surgery studies was an order of magnitude greater than weight loss in pharmaceutical or diet studies [5]. The TA cited a weight loss at 1 or 2 years of 20 to 40 kg in surgical studies versus 2 to 5 kg in pharmaceutical studies [5]. Extremely obese persons often do not benefit from nonsurgical treatments for weight loss and weight maintenance [5]. In a study of the National In-patient Survey (NIS), Pope et al. [6] reported that the rate of bariatric surgery procedures increased from 2.7 to 6.3 per 100,000 adults from 1990 to 1997. During the same period, gastric bypass surgery as a percentage of all bariatric surgeries in the US increased from 54% to 84% [6]. Weight loss surgery may be an option for certain selected patients with clinically severe obesity (BMI ≥ 40 or ≥ 35 with comorbid conditions), when less invasive methods of weight loss treatment have failed and the patient is at high risk for obesity-associated morbidity or mortality [2]. Based on this increase in obesity and the increased rate of bariatric surgery, the Centers for Medicare Services (CMS) elected to ask the Medicare Coverage Advisory Committee, in a public forum, to review and assess the evidence for bariatric surgery.