Abstract
THE most variable component of the body is fat; in comparison (with that of the whole body) the composition of the fat-free body is relatively constant. The constancy of fat-free body composition is the basis for estimation of whole-body composition by several indirect methods in animals and humans. This constancy-of-composition concept is utilized in genetics, meat science, medicine, nutrition, physical education, physical anthropology and physiology. The accuracy and precision of estimates of protein deposition from N balance, and of fat and the fat-free body content from body water, density and body potassium measurements are related to the constancy of fat-free body composition. Some have concluded that the fat-free body is variable in composition. They recommend a multicomponent approach, estimating two or more components of the body by independent methods (Anderson, 1963). Others have stressed the utility of the two-component system (Forbes and Hursh, 1963) and still others have argued that the entire body is remarkably uniform in composition at a given body weight (Reid et al., 1968a). Copyright © 1971. American Society of Animal Science . Copyright 1971 by American Society of Animal Science.