Document Type



In the consideration of body composition, it is important to distinguish between variables that are measured and those that are estimated and to know the magnitude and the sources of the associated errors. The measurement errors of densitometry are small, but the errors of the estimates of body composition variables from body density are incompletely known, and probably substantial, except in young men. Equations to estimate body composition variables from body density are now available for other age-and sex-groups; presumably use of these will reduce the errors of estimation. A major limitation of densitometry is its inapplicability to children younger than 8 years. As an alternative, total body water can be measured, and used in combination with the water content of fat-free mass, to estimate fat-free mass and percent body fat, although the water content of fat-free mass has not been measured in children. Skinfold thicknesses are predictive of body fatness, but the conceptual limitations associated with using the thicknesses of compressed skin and adipose tissue in combination with uncompressed circumferences, to estimate tissue areas in cross-sections of the limbs should be recognized.