Comparison of Body Composition Variables between Post-Bariatric Surgery Patients and Non-Operative Controls

Background: Since bariatric surgery results in massive weight loss, it may be associated with a disproportionate decrease in lean body mass.Objective: To evaluate body composition in post-bariatric surgery patients who had a successful weight loss at 12 months (>50% excess weight loss) with comparisons to healthy controls who were matched for age, sex and BMI.Methods: This is an observational analytic study using data from post-bariatric surgery patients who had laparoscopic Roux-en-Y gastric bypass (RYGB) or laparoscopic sleeve gastrectomy (SG) at King Chulalongkorn Memorial Hospital. Patients who had percentage excessive weight loss (%EWL) >50% and achieved a BMI of <30 kg/m(2) within 12 months after the surgery were included. Non-operative healthy controls matched for sex, age, and BMI (1:1) were recruited. The 12-month post-bariatric surgery BMI was used to match the BMI of the control subjects. A single bioelectrical impedance analysis (BIA) (Inbody 770) machine was used for the entire study.Results: Sixty participants were included in this study. There are 30 post-bariatric surgery patients (female n = 19, male n = 11) and 30 non-operative controls (female n = 19, male n = 11). The 12-month post-bariatric surgery patients had lower percentage of body fat (PBF) (30.6% vs 35.9%, P-value .001) and trunk fat mass (10.3 vs 12.4 kg, P-value .04) than non-operative controls. The 12-month post-bariatric surgery patients also were found to have more soft lean mass (SLM) (47.7 vs 39.9 kg, P-value .001), fat free mass (FFM) (51.1 vs 42.3 kg, P-value .001), skeletal muscle mass (SMM) (27.5 vs 23 kg, P-value .003), and trunk lean mass (21.2 vs 19 kg, P-value .02).Conclusion: Despite the significant reductions in all body composition variables in post-bariatric surgery patients at 12-month follow-up, both fat free mass and skeletal muscle mass were found to be higher in the surgical patients compared to the control group.