Body composition. Methods of estimation and effect upon performance.

The assumption that is implicit in nearly all methods for determining body composition is that the fat-free body has a constant composition and that fat content can vary from some minimal amount to over 70 per cent. Fat estimations, however, are almost always indirect and are based upon estimating some fat-free component of the body. Some fifteen different methods are described in terms of the principle involved, the cost, and the applicability for routine use. A review is presented of a large number of regression equations that have been developed to predict body density from many types of anthropometric equations. The accuracy or comparative accuracy of body composition methods cannot be evaluated with human subjects. Methods can be validated only by using the method on an animal model, then performing chemical analyses on the same animal. Data of this type are limited.