Weight Loss and Body Composition During the First Postoperative Year of a Laparoscopic Roux-En-Y Gastric Bypass

Background Weight loss in patients undergoing gastric bypass should be primarily from fat mass (FM), minimizing the fat-free mass (FFM) loss. The aim of this study was to analyze changes in body weight and body composition during the first postoperative year in 50 morbidly obese patients undergoing a Laparoscopic Roux-en-Y gastric bypass (LRYGBP) at the Obesity Clinic of the ABC Medical Center. Methods Patient’s weight and body composition were obtained before surgery and 1 year later using bioelectrical impedance analysis (BIA). Weight, FM, FMM, and total body water (TBW) were measured before and 1 year after surgery. Changes in body composition were particularly analyzed. Results There were 29 females and 21 males with mean age of 41 ± 12 years. Mean BMI before surgery and 1 year after surgery was 44.4 ± 7.4 kg/m² and 28.3±4.3 kg/m², respectively. The percentage of excess body weight loss at the 1-year period was 86% for women and 79.6% for men. The percentage of FM before surgery was 47.7 ± 5.1, and 1 year later it was 28.8 ± 8. The percentage of FFM was 66.5 ± 16.5 before surgery and 58.3 ± 13 at 1 year. Conclusions There is a significant weight loss in patients undergoing LRYGBP. Weight loss mainly occurs as a consequence of reduction in the FM with less impact on the FFM.