Background: Historically, preoperative weight loss has been encouraged for patients undergoing gastric bypass surgery to decrease liver mass, technically facilitating the procedure. In an earlier prospective randomized trial investigating effects of preoperative weight loss on patients' clinical outcomes, we reported no differences in postoperative complications or weight-loss profiles at 6-month followup. This article demonstrates results of the same study, with 1-year followup. Study Design: One hundred consecutive patients in an 18-month period preparing to undergo gastric bypass surgery at Stanford University Medical Center were selected. Fifty patients were randomly assigned to lose 10% or more of their excess body weight preoperatively, and 50 patients were assigned to no preoperative weight-loss requirements. After 1 year, patient demographics and data on postoperative complications, cure or improvement of comorbidities, and differences in weight-loss profiles were collected. Results: At 1 year, the 2 groups had similar preoperative demographics and body mass indexes (BMIs). Patients in the weight-loss group, on average, lost 8.2% of their excess body weight preoperatively compared with the nonweight-loss group, which gained 1.1% (p = 0.007). After a year, the patients in both arms of the study showed no difference in weight, BMI, excess weight-loss, and number of remaining comorbidites. But when patients were divided according to those who had lost at least 5% of their excess body weight preoperatively, the 1-year results for excess weight-loss, weight, and BMI were much lower for the weight-loss group. Conclusions: Preoperative weight loss in patients undergoing gastric bypass surgery is safe and feasible. It should be encouraged, because it will markedly improve longterm weight loss.
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