Four-compartment cellular level body composition model: Comparison of two approaches

SHEN, WEI, MARIE-PIERRE ST-ONGE, ANGELO PIETROBELLI, JACK WANG, ZIMIAN WANG, STANLEY HESHKA, AND STEVEN B. HEYMSFIELD. Four-compartment cellular level body composition model: comparison of two approaches. Obes Res. 2005;13:58-65. Objective: The aim of this study was to develop and compare two DXA-based four-compartment [body weight body cell mass (BCM) + extracellular fluid (ECF) + extracellular solids (ECS) + fat] cellular level models. Research Methods and Procedures: Total body potassium (TBK) model: BCM from TBK by whole-body counting-ECFTBK = LST - [BCMTBK + 0.73 X osseous mineral (Mo)]. Bromide model: ECF from sodium bromide dilution-BCMBROMIDE = LST - (ECFBROMIDE + 0.73 X Mo); Mo and LST measurements came from DXA. The two approaches were evaluated in 99 healthy men and 118 women. Results: BCM estimates were highly correlated (r = 0.97, p < 0.001), as were ECF estimates (r = 0.87, p < 0.001); a small statistically significant mean difference was present (mean SD; BCMTBK model, 30.4 +/- 8.9 kg; BCMBROMIDE, 31.4 +/- 9.3 kg; Delta = 1.0 +/- 2.8 kg; p < 0.001; ECFTBK, 18.5 +/- 4.2 kg; ECFBROMIDE, 17.5 +/- 3.6 kg; Delta = 1.0 +/- 2.8 kg; p < 0.001). A high correlation (r 0.97, p < 0.001) and good agreement (38.9 +/- 9.5 vs. 38.9 +/- 9.5 kg; Delta = 0.0 +/- 2.4 kg; p = 0.39) were present between TBW, derived as the sum of intracellular water from TBK and ECW from bromide, and measured TBW by (H2O)-H-2 dilution. Discussion: Two developed four-compartment cellular level DXA models, one of which is appropriate for use in most clinical and research settings, provide comparable results and are applicable for BCM and ECF estimation of subject groups with hydration disturbances.