Longitudinal body composition changes due to dialysis

Nutritional status remains a powerful predictor of outcome in the dialysis population. High body mass index (BMI) seems protective, but which body compartment (fat or lean mass) confers this protection remains unclear. DESIGN, SETTING, PARTICIPANTS, MEASUREMENTS: This was a longitudinal study (n = 60; n = 46 completed) examining changes in body composition in incident peritoneal dialysis (PD) and hemodialysis (HD) patients over 12 months. We measured total body protein (TBP) by in vivo neutron activation, expressed as nitrogen index (NI), and lean body mass (LBM) and total body fat (TBF) by dual-energy x-ray absorptiometry. Visceral and subcutaneous fat areas (SFAs) were determined from computed tomography. Comparisons were made between different BMI groups and dialysis modalities. RESULTS: No significant change was found in TBP, NI, or TBF. The obese group (BMI >30) had an increase in all mean LBM parameters with a significant increase in NI compared with normal-weight and the overweight group. This increase in NI remained significant after multivariate analysis beta coefficient (0.08). PD patients had the greatest increase in TBF, with a significant increase in visceral fat (VFA:SFA ratio beta coefficient = 0.23). CONCLUSIONS: Obese patients showed preservation of TBP compared with normal- and overweight patients, suggesting that energy storage as fat mass is of value in the dialysis population.