Postoperative Resting Metabolic Rate and Successful Weight Loss After Roux-en-Y Gastric Bypass

Objective To analyze whether changes in RMR 6 months after RYGB could be a predictor of weight loss on late follow-up.Methods Prospective study of 45 individuals submitted to RYGB in a university tertiary care hospital. Body composition was evaluated by bioelectrical impedance analysis and RMR by indirect calorimetry before (T0), 6 (T1), and 36 months (T2) after surgery.Results RMR/day was lower in T1 (1.552 +/- 275 kcal/day) than in T0 (1734 +/- 372 kcal/day; p < 0.001) with a return to similar values at T2 (1.795 +/- 396 kcal/day; p < 0.001). In T0, there was no correlation between RMR/kg and body composition. In T1, there was a negative correlation between RMR and BW, BMI, and % FM, and a positive correlation with % FFM. The results in T2 were similar to T1.There was a significant increase in RMR/kg between T0, T1, and T2 (13.6 +/- 2.2 kcal/kg, 16.9 +/- 2.7 kcal/kg, and 19.9 +/- 3.4 kcal/kg) in the total group and according to gender. Eighty percent of the patients who had increased RMR/ kg >= 2 kcal at T1 achieved > 50% EWL in T2, particularly in women (odds ratio: 27.09, p < 0.037).Conclusions The increase in RMR/kg after RYGB is a major factor related to a satisfactory % excess weight loss on late follow-up.

Automated summary

This study examined the relationship between changes in resting metabolic rate (RMR) after Roux-en-Y gastric bypass (RYGB) surgery and weight loss on long-term follow-up. The results showed that RMR was significantly lower at 6 months post-surgery compared to pre-surgery levels, but returned to similar values at 36 months. There was a positive correlation between RMR and percentage of fat-free mass, and a negative correlation with body weight, body mass index, and percentage of fat mass. The increase in RMR/kg after RYGB was found to be a major factor associated with satisfactory weight loss on long-term follow-up.