Earthman CP|Beckman TR|Sibley SD|Thomas W|Beckman LM|Mager JR|Ikramuddin S|Kellogg TA|Weijs PJM|Kunkel SA
Published at the 9th International Symposium on In Vivo Body Composition Studies, Hangzhou, China
OBJECTIVE: To evaluate bioelectrical impedance analysis (BIA)-derived parameters for body composition and clinical outcomes assessment in Roux-en-Y gastric bypass (RYGB) patients.
SUBJECTS/METHODS: Women (BMI: 46.7±6.4 kg/m2) undergoing RYGB were measured pre-operatively (n=29) and at 6 weeks (n=20) and 1 year (n=20) post-surgery using multiple dilution and multi-frequency BIA.
RESULTS: Vector length (VL,50KHz) was negatively correlated with weight and fat-free-mass (FFM) at all time points and with muscle strength at pre-op and 1 year. At 6 weeks, phase angle (PA,50KHz) and the 200/5 kHz impedance ratio (IR) were correlated with strength (r=0.53 and r=-0.63, respectively). The 12-month changes in total body water (TBW)/weight and extracellular water/weight were correlated positively with IR, and negatively with PA and VL change. Pre-operative IR, PA, and VL predicted weight (R2=0.639), FFM (R2=0.368), BMI (R2=0.554), and TBW/weight (R2=0.430) at 1 year by multiple linear regression. VL was greater among subjects with lower weight (P=0.002), FFM (P=0.006), BMI (P=0.008), and intracellular water (P=0.011) by paired t-tests at pre-op. The resistance-reactance graph vectors were normal for obese individuals and the percentage within the 75% tolerance ellipse increased from 31% pre-operatively to 78% at 1 year.
CONCLUSION: BIA parameters may be useful for assessing body composition in RYGB patients.