A Comparison of Body Composition Techniques

A variety of strategies have been employed to estimate body composition, such as near-infrared spectral analysis, and arm-to-arm and leg-to-leg bioimpedance analysis (BIA) systems. With BIA, an electrical current of known frequency is transmitted across the tissue bed; the impedance to this transmission is related to the conduction properties of the tissue, which, in turn, is used to estimate fat-free and fat masses.1 Using near-infrared spectroscopy, interactance is based on the laws of light absorption and reflection. Depending on the absorptive and scattering properties of the tissue, when this light strikes the material, the energy is reflected, absorbed, or transmitted. In essence, the energy transmitted is scattered and reflected back out, and thus provides us with the chemical composition of the sample. A combination of skin and subcutaneous fat thickness was hypothesized to allow optimal penetration and interactance of the low level of infrared radiation.2 The purpose of the present investigation was to explore the validity of the leg-to-leg BIA, arm-to-arm BIA, and near-infrared spectral analysis models by comparing the respective estimates of total body fat with those obtained via dual-energy X-ray absorptiometry (DXA).