Table 3.

Comparison of relative variability of body component ratios.

Ratio with simplified model	E/I value
	0.8	0.9	0.95	1.0	1.1	Variability
FFM density = (1.569 + 1.16 × E/I)/(1.396 + 1.08 × E/I)	1.105	1.103	1.103	1.102	1.101	0.36%
TBK/BCM = 106.4 + 2.8 × (E/I)	108.6	108.9	109.1	109.2	109.5	0.81%
TBW/FFM = (1 + E/I)/(1.569 + 1.16 × E/I)	0.721	0.727	0.730	0.733	0.738	2.3%
TBW/LST = (1 + E/I)/(1.488 + 1.080 × E/I)	0.765	0.772	0.776	0.779	0.785	2.6%
Ms/TBW = (0.0162 + 0.0095 × E/I)/(1 + E/I)	0.0132	0.013	0.0129	0.0129	0.0127	3.9%
TBPro/FFM =(0.445 + 0.069 × E/I)/(1.569 + 1.16 × E/I)	0.200	0.194	0.191	0.188	0.183	8.9%
TBK/FFM = (152 + 4 × E/I)/(1.569 + 1.16 × E/I)	62.2	59.5	58.3	57.2	55.0	12.3%
BCM/FFM = 1.429/(1.569 + 1.16 × E/I)	0.572	0.547	0.535	0.524	0.502	13.1%

Body component ratios: BCM/FFM, ratio of body cell mass to fat-free mass (in kg/kg); FFM density, fat-free mass density (in kg/L); Ms/TBW, ratio of soft-tissue minerals to total body water (in kg/kg); TBK/BCM, ratio of total body potassium to body cell mass (in mmol/kg); TBK/FFM, ratio of total body potassium to fat-free mass (in mmol/kg); TBPro/FFM, ratio of total body protein to fat-free mass (in kg/kg); TBW/FFM, ratio of total body water to fat-free mass (in kg/kg); TBW/LST, ratio of total body water to lean-soft tissue (in kg/kg).

Abbreviation: E/I, ratio of extracellular water to intracellular water (in kg/kg).

Variability of body component ratio: For instance, the relative variability of TBW/FFM ratio can be calculated as [(TBW/FFM at E/I 1.1) – (TBW/FFM at E/I 0.8)]/(TBW/FFM at E/I 0.95) = (0.738 − 0.721)/0.730 = 2.3%.