Bariatric Surgery: Crossing a Body Mass Index Threshold

As many as 5% of adults in developed nations now have extreme obesity, characterized by a body mass index (BMI) of 40 kg/m2 or more (1). These individuals have a mortality rate that is at least double that of individuals with a BMI in the desirable range of 18.5 kg/m2 to 24.9 kg/m2 (2). More than 40 years of research has shown that surgical intervention, particularly the gastric bypass, is the treatment of choice for extremely obese individuals who cannot control their weight with traditional methods, such as lifestyle modification or pharmacotherapy (3, 4). Bariatric surgery also is indicated for individuals with BMIs of 35.0 kg/m2 to 39.9 kg/m2 who have comorbid conditions, including type 2 diabetes, hyperlipidemia, and sleep apnea (5, 6). Both the gastric bypass and the newer laparoscopic adjustable gastric banding improve these conditions (3, 4). The gastric bypass is generally considered to be the more effective of the 2 procedures, but it is associated with higher mortality than laparoscopic adjustable gastric banding (4). The report by O'Brien and colleagues (7) in this issue provides the strongest evidence to date of the benefits of bariatric surgery relative to lifestyle modification and pharmacotherapy. The authors successfully completed a 2-year randomized, controlled trial in which 80 obese adults (BMI, 30.0 kg/m2 to 34.9 kg/m2) were assigned to laparoscopic adjustable gastric banding or treatment by a very-low-calorie diet combined with the weight loss medication orlistat. Patients in both groups lost 13.8% of initial weight during the first 6 months. The 2-year assessment, however, revealed the clear superiority of laparoscopic adjustable gastric banding. Surgically treated patients continued to lose weight, reaching a 21.8% reduction at the second year. By contrast, participants in the nonsurgical group regained weight steadily after the sixth month, concluding the trial with a loss of only 5.5%. Surgically treated patients also had statistically significantly greater improvements in cardiovascular risk factors and quality of life than did those in the comparison group. In addition to its several strengths, O'Brien and colleagues' study has 2 important limitations that concern the nonsurgical intervention. First, the authors did not adequately describe the regimen of lifestyle modification and drug therapy that they used after the first 6 months, thus limiting other investigators' ability to replicate the study. Second, the authors did not provide a structured weight loss maintenance program that included twice-monthly contact with patients. Frequent contact with patients who are trying to lose weight facilitates long-term weight control (8). Anderson and colleagues (9), for example, treated 85 severely obese patients with a very-low-calorie diet, exercise, and weekly group support sessions. The 63 patients (74%) who completed the 2-year program sustained a weight loss of 15.2% at the end of this time. Similarly, at least 2 trials of orlistat (10, 11) and 1 trial of sibutramine (12), all of which combined medication and lifestyle modification, obtained 8% to 10% reductions in initial weight at 2 years. These results are typical for programs that combine pharmacotherapy with lifestyle modification. The biggest surprise in O'Brien and colleagues' report concerned not the patients' weight losses but the patients themselves. The authors selected participants with a BMI of 30.0 kg/m2 to 35.0 kg/m2, a mild to moderate degree of obesity for which bariatric surgery is not currently indicated. The authors note that they did not study patients with a body mass index greater than 35 kg/m2 because current observational data suggest that outcomes after nonsurgical treatment were unlikely to be equal to those after surgical care for these patients (7). Excluding persons with BMIs of 35.0 kg/m2 to 39.9 kg/m2 seems odd, given that the World Health Organization (5) and other scientific bodies (6) have recommended that the combination of lifestyle modification and pharmacotherapy be considered with such individuals before considering surgery. O'Brien and colleagues' study was approved by an institutional review committee for research involving human participants. A critical concern is whether the study's participants, with a BMI of 30 kg/m2 to 35 kg/m2, were fully aware that they were to receive a surgical procedure that current guidelines do not recommend for persons in this weight range. What effect will O'Brien and colleagues' crossing the BMI threshold have on patients and providers? Undoubtedly, the report will increase the public's already substantial and growing interest in bariatric surgery. We hope, however, that the findings will not cause primary care providers or their patients to overlook the positive health benefits of a 5% to 10% weight loss achieved with lifestyle modification. Weight losses of this size, in mildly to moderately obese individuals, reduce hypertension (13) as well as the risk for developing type 2 diabetes (14). In addition, lifestyle modification is far more available to obese individuals than is bariatric surgery, which (in the United States) appears to be most accessible to individuals from higher-income families who have private health insurance (15). We hope that O'Brien and colleagues' study will stimulate further carefully controlled research on the relative risks and benefits of bariatric surgery when used in persons with mild to moderate obesity. This research will present institutional review committees with complex issues, given the contrast between the current guidelines and the results of O'Brien and colleagues' study. Committees must address the balance of potential benefit and potential harm from bariatric surgery. A key research need is to identify, among mildly to moderately obese individuals, persons who would benefit the most, as well as the least, from surgical intervention. The selection of appropriate individuals will require practitioners to move beyond the measurement of BMI to assess abdominal (that is, visceral) adiposity and to calculate the patient's overall cardiovascular risk. Currently, mildly obese individuals with type 2 diabetes would seem to have the most to benefit from bariatric surgery, given the dramatic amelioration of the disorder (after surgery) in persons with BMIs of 35 kg/m2 or more (3, 4). Conversely, practitioners and patients must recognize that not all comorbid conditions respond equally to bariatric surgery and that some, in fact, may be better managed with medication. The long-term results of the Swedish Obese Subjects Study, for example, indicate that surgically induced weight loss is not an effective treatment for hypercholesterolemia (16). Similarly, we do not think that it is appropriate to use bariatric surgery as a treatment for significant psychosocial problems associated with obesity, as was done in O'Brien and colleagues' study. Psychotherapy and pharmacotherapy are proven effective treatments for mental health disorders; bariatric surgery is associated with varying psychiatric outcomes, some of which may be negative (17). The other side of the riskbenefit calculation is risk. We need better ways of capturing short- and long-term morbidity and mortality outcomes, particularly if surgery is to be considered for mildly obese individuals (in whom the cardiovascular risks posed by obesity are generally low). Short-term mortality associated with laparoscopic adjustable gastric banding is frequently reported as 0.05% (7). A recent meta-analysis, however, found in controlled trials that adjustable gastric banding was associated with short-term (that is, 30 days) mortality of 0.4%. Similarly, although the short-term mortality rate for gastric bypass is often cited as 0.5%, a recent study observed a rate of 1.9% among low-volume surgeons (18). Long-term outcomes of both laparoscopic adjustable gastric banding and gastric bypass must be carefully tracked, not only to determine safety but also to assess total costs of these procedures. A 6-year cost analysis of the Swedish Obese Subjects Study, for example, revealed significantly more hospital days (and total hospital costs) for surgically treated participants than for control participants (19). The study by O'Brien and colleagues would have benefited from an economic analysis of the 2 interventions, which would have captured the costs of late-term laparoscopic revisions in 4 patients who developed prolapse of the posterior gastric wall through the band. While up to one third of the population in developed nations now has obesity in some degree, most people still are not obese. We need to expend far more resources on preventing these individuals, particularly children, from becoming obese. Although surgical, pharmacologic, and lifestyle interventions can assist those who are already obese, we need innovative public policy initiatives and wide-scale environmental interventions that will reduce the numbers of persons who require these treatments (20). Developed nations cannot afford for any more of their citizens to cross another BMI threshold, whether it is 25 kg/m2, 30 kg/m2, or 40 kg/m2.