The most accurate method to assess body composition involves chemical analysis of the body. However, as this can be done only after death, it is of limited value in the assessment of body composition in the living. Fortunately, several indirect methods for assessment have been developed for estimation in living subjects. The most common are densitometry (underwater weighing or air displacement), anthropometry (measures of body girths, breaths, and/or skin fold thickness), and bioelectrical impedance (measures of opposition to a weak electrical current introduced into the body). Of these, densitometry is considered the most accurate because its estimation is based on results obtained from direct chemical analysis of cadavers. However, it cannot be exact for given individuals because most will differ somewhat from the cadavers that were analyzed.
Consequently, there will always be a small absolute error (perhaps 2-3%) that must be considered when these measures are used. This, of course, is of little concern to your health when relative measures are compared, i.e., in a study in which before and after measures are compared, because the error is constant. Typically, anthropometry and bio-impedance methods involve more absolute error, as their estimations are based on results from densitometric analyses, i.e., they are estimates of an estimate. However, they are widely used because they are easy and the necessary equipment is both portable and relatively inexpensive. Other more sophisticated body composition measures are possible including magnetic resonance imaging and dual energy X-ray absorptiometry but are primarily used in research settings as the equipment necessary is expensive.
-
Archives
-
Meta