The effect of a low-carbohydrate, high-protein diet on post laparoscopic gastric bypass weight loss: a prospective randomized trial

BACKGROUND: Laparoscopic gastric bypass has become the standard surgical treatment for severe obesity in the United States. Less clear is what diet should be followed by these patients after surgery to maximize their weight loss. METHODS: Patients undergoing laparoscopic gastric bypass procedures for morbid obesity were randomly assigned to either a low-fat control diet based on American Heart Association recommendations or a low-carbohydrate, high-protein diet based on the South Beach Diet. One-on-one diet counseling with a bariatric nutritionist was provided preoperatively, postoperatively while in the hospital, and at postoperative clinic visits during the 12-month follow-up period. Investigators were blinded to diet assignment. Body composition including Body Mass Index (BMI) was recorded preoperatively and during postoperative visits at 3, 6, and 12 months. RESULTS: Thirty-two patients were included in the analysis with 13 control and 19 low-carbohydrate, high-protein subjects. No demographic or clinical preoperative variables, including preoperative BMI, showed statistical differences between the two groups. Both groups demonstrated significant yet similar weight loss both by reduction in BMI (at 12 months, low fat diet, -14.0 +/- 5.5% versus low carbohydrate, -17.0 +/- 4.5%; P = 0.15) and excess body weight lost (at 12 months, low-fat diet, -60.3 +/- 15.3% versus low carbohydrate, -59.6 +/- 13.0%; P = 0.96). CONCLUSIONS: Based on this limited prospective study, no weight loss advantage is observed in substituting a low-carbohydrate, high-protein diet in place of a standard low-fat diet in patients who have undergone laparoscopic gastric bypass surgery.