ABSTRACT
When it comes to body composition assessment and availability of methods, exercise specialists, health practitioners, and clinicians must consider the demographic characteristics of their clients. Age, ethnicity, sex, degree of adiposity, and physical activity are a few important factors in the selection of appropriate methods and instruments for obtaining the most accurate results. Many methods rely on prediction equations developed from validation groups with specific characteristics. When these instruments and equations are used on individuals or groups with characteristics different from those of the validation group, the accuracy of the results may be questioned. It is also important when selecting a body composition method to assess the relative worth of the method in terms of the criterion or reference method used to evaluate the technique of choice. Acceptable reference or criteria methods include hydrodensitometry (underwater weighing), hydrometry (isotope dilution), or dual energy x-ray absorptiometry (DXA). These reference methods, however, are not without errors and assumptions, and cannot be considered “gold standards” for
in vivo
body composition assessment. Reference methods typically focus on the body as a two-compartment system consisting
of the fat-free mass (FFM) and fat mass (FM), and can be of limited use for individuals whose fat-free mass density and hydration levels differ from the assumed values for this model. Methods that have been validated against the reference two-compartment model will systemically underestimate body fatness for American Indian women, black men and women, and Hispanic women, because the average density of the FFM in these groups exceeds the assumed value of 1.1 g/cc. This can be avoided, however, if one uses methods that have been validated against a multi-compartment model which makes corrections for differences in the hydration level and bone mineral content of the FFM.
