RESUMO
BACKGROUND: Weight loss and body composition changes after Roux-en-Y gastric bypass (RYGB) may influence resting energy expenditure (REE). The effect of lower REE after the procedure on long-term weight remains to be elucidated. OBJECTIVE: To evaluate the effects of RYGB on REE and body composition 6 months after RYGB and to find out whether postsurgery REE affects weight at 12 and 18 months SETTING: Tertiary referral hospital, southern Brazil METHOD: A prospective study involving 30 RYGB patients aged>18 years was performed. Body composition was evaluated by X-ray absorptiometry and REE by indirect calorimetry. All patients were assessed before RYGB and 6 months postoperatively. Further analysis of weight was carried out at 12 and 18 months. RESULTS: Baseline body mass index was 49±9 kg/m² and mean weight was 128±19 kg, half of which comprised fat mass (50±5%). Baseline mean REE was 2297±182 kcal/d. The percent total weight loss was 26±7%, 32±9%, and 34±9% at 6, 12, and 18 months, respectively. The percent excess weight loss gradually increased from 54 ± 12% at 6 months, to 67 ± 18% at 12 months, and 71 ± 19% at 18 months. REE was significantly lower at follow-up (-405±108 kcal/d; P<.001). Furthermore, an inverse correlation between REE at 6 months and percent excess weight loss at 18 months (r =-.612; P = .035) was observed in the subgroup of patients whose REE decreased>405 kcal/d at 6 months. CONCLUSION: Patients undergoing RYGB who had a substantial drop in REE at 6 months may exhibit less long-term weight loss.
