Body composition from fluid spaces and density: analysis of methods. 1961.

Abstract

The gross composition of the human body is regarded as a mixture of water, lipids, and fat-free solids, the last consisting mainly of protein and inorganic mineral.The proportions of the se constituents are important biological variable s, both in normal and diseased state s of the body, but their evaluation has been subject to considerable uncertainty.Total body water is the only constituent amenable to direct measurement in vivo, whereas the remaining constituents can only be estimated indirectly from the proportion of body water or from the whole -body density.The indirect methods for estimating fat and fat -free solids are subject therefore to both experimental error and biological variability.The consequent uncertainty in the estimates depends largely on the assumptions that are inherent in the .methods that are used.Each of the procedures for estimating body composition that is based on body water, corporal density, or a combination of these measurements is examined for its basic premises, its formulation, and the limits of its validity.Formulas are derived for calculating total depot fat in humans and for calculating the standard deviation.In general, the uncertainty in fat estim'ated from density or water is about 4% of body weight, whereas combined body water and density yield an error of 2%.