OBJECTIVE:: To compare and describe the weight loss outcomes from gastric bypass and gastric band so as to define the variation of excess weight loss (EWL) among individual patients, the time to onset of effect, and the durability of weight loss in severely obese adults. SUMMARY BACKGROUND DATA:: Gastric bypass and gastric band are the most common operations for obesity performed in the United States, but few reports have compared these 2 procedures. METHODS:: Patients (N = 1733, aged 18-65 years) met National Institutes of Health criteria for obesity surgery and underwent either gastric bypass or gastric band between March 1997 and November 2006. The selection of bypass versus band was based on patient/ surgeon discussion. The evaluable sample consisted of 1518 patients. The percentage of EWL was assessed over 2 years. Successful weight loss was defined a priori as ≥40% EWL in each of four 6-month postoperative measurement periods. The analyses included a mixed model and generalized estimating equation (GEE) model with repeated measures. Odds ratios and descriptive analyses were also provided. RESULTS:: Gastric bypass was associated with less individual variation in weight loss than gastric band. Both procedures were associated with a significant EWL benefit (Treatment Group effect P < 0.0001), but they differed in terms of time to effect (Treatment Group × Period interaction effect P < 0.0001). The mean EWL for gastric bypass was greater at each measurement period (6, 12, 18, 24 months) compared with gastric band (P < 0.0001). Furthermore, at each of the postoperative measurement periods within each treatment group (bypass and band), the mean EWL was greater for those who had preoperative body mass index (BMI) ≤50 kg/m than for those who had preoperative BMI >50 kg/m (P < 0.0001). Gastric bypass was consistently associated with a greater likelihood of at least a 40% EWL in each of the 6-month postoperative measurement periods (GEE, P < 0.0001). The odds ratio estimates at months 6, 12, 18, and 24 were 18.2, 20.6, 15.5, and 9.1, respectively. Despite these clinically meaningful outcome differences, nearly all (≥93%) bypass and band patients who had ≥40% EWL at 6,12, or 18 months postoperatively maintained at least this level of success at 2 years. CONCLUSIONS:: Gastric bypass produced more rapid, greater, and more consistent EWL across individuals over a 2-year postoperative period than gastric band.
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