Noninvasive Evaluation of Abdominal Fat and Liver Changes Following Progressive Weight Loss in Severely Obese Patients Treated with Laparoscopic Gastric Bypass

Background Obesity is a chronic complex disease, consequence of an unbalance between energy intake and expenditure and of the interaction between predisposing genotype and facilitating environmental factors. The aim of the study was to evaluate body composition, abdominal fat, and metabolic changes in a group of severely obese patients before and after laparoscopic gastric bypass (LGBP) at standardized (10% and 25%) total weight loss. Methods Twenty-eight patients (14 M, 14 F; age 41.71 ± 6.9 years; body mass index (BMI) 49.76 ± 5.8 kg/m 2 ) were treated with laparoscopic gastric bypass. All evaluations before surgery and after achieving ~10% and ~25% weight loss (WL). Body composition was assessed by bioimpedance analysis; resting metabolic rate (RMR) was measured by indirect calorimetry. Results Body weight, BMI, and waist circumference significantly decreased at 10% and 25% WL. We observed a significant reduction of both RMR (2,492 ± 388 at entry vs. 2,098 ± 346.6 at 10% WL vs. 2,035 ± 312 kcal per 24 h at 25% WL, p = 0.001 vs. baseline) as well as of RMR corrected for fat-free mass (FFM; 35.7 ± 6.7 vs. 34.9 ± 9.0 at 10% WL vs. 33.5 ± 5.4 at 25% WL kilocalorie per kilogram FFM × 24 h, p = 0.041 vs. baseline). Body composition analysis showed a relative increase in FFM and a reduction of fat mass at 25% WL. A significant reduction in blood glucose, insulin, homeostasis model assessment index was observed. Ultrasonography showed a marked decrease in the signs of hepatic steatosis. Conclusion In conclusion, our study confirms that LGBP is a safe procedure in well-selected severely obese patients and has early favorable effects on both metabolic parameters and body composition. Longer-term observations are required for in-depth evaluation of body composition changes.