Abstract
BACKGROUND Weight loss is the sum of fat and lean mass loss. The aim of this study was to examine whether there are differences between 2 surgical procedures, laparoscopic sleeve gastrectomy (LSG) and laparoscopic Roux-en-Y gastric bypass (LRYGB), in terms of their effect on body composition and energy metabolism. In addition, the predictive value of preoperative body composition and energy metabolism on postoperative outcome was evaluated. SETTING All procedures were performed by the same surgeon (RP) at the St. Claraspital Basel in Switzerland. Calorimetry and DEXA were carried out at the same institution (Interdisciplinary Center of Nutritional and Metabolic Diseases, St. Claraspital Basel). METHODS Forty-two morbidly obese, mainly female (85%), nondiabetic and diabetic (50%) patients (body mass index [BMI]: 43.9 kg/m(2)±1.3) before and 17±5.6 months after LSG (n = 23) and LRYGB (n = 19) were examined. Body composition was analyzed by dual-energy X-ray absorptiometry (DEXA) and resting energy expenditure (REE); fat and carbohydrate oxidation was determined by indirect calorimetry. RESULTS Follow-up was 100%. Excessive BMI loss (EBMIL) was 64.4% in the LSG group and 76.4% in the LRYGB group (P<.046). In both groups total fat and muscle mass decreased significantly compared with baseline (P<.001) and the percentage of muscle mass per kilogram of weight increased postoperatively (results not significant). REE decreased (P<.001) and REE per kilogram of weight increased significantly (P<.003) compared with baseline. Carbohydrate oxidation remained stable in both groups, and fat oxidation decreased significantly (P<.001) compared with baseline. In diabetic patients compared with nondiabetic patients there were no statistically significant differences in REE, substrate oxidation, or reduction in truncal fat. Postoperatively, lean mass was higher in diabetic patients (P = .037). Preoperative indirect calorimetry and DEXA results were of no predictive value for outcome. CONCLUSION Changes in REE and body composition were equal after both procedures in a bariatric population mainly consisting of women. No predictors for amount of weight loss could be found.
