Body composition (particularly body fat percentage) can be measured in several ways. The most common method is by using a set of measurement calipers to measure the thickness of subcutaneous fat in multiple places on the body. This includes the abdominal area, the subscapular region, arms, buttocks and thighs. These measurements are then used to estimate total body fat with a margin of error of approximately four percentage points.
Another method is bioelectrical impedance analysis (BIA), which uses the resistance of electrical flow through the body to estimate body fat.
A technique for measuring body composition has been developed using the same principles as under water weighing. The technique uses air, as opposed to water, and is known as air displacement plethysmography (ADP). Subjects enter a sealed chamber that measures their body volume through the displacement of air in the chamber. Body volume is combined with body weight (mass) in order to determine body density. The technique then estimates the percentage of body fat and lean body mass (LBM) through known equations (for the density of fat and fat free mass).
Body composition measurement with Dual Energy X-ray Absorptiometry (DEXA) is used increasingly for a variety of clinical and research applications. Total body or estimated total body scans using DEXA give accurate and precise measurements of BMD and body composition, including bone mineral content (BMC), bone mineral density (BMD), lean tissue mass, fat tissue mass, and %fat results [4]. These measurements are extremely reproducible, making them excellent for monitoring pharmaceutical therapy, nutritional or exercise intervention, sports training &/or other body composition altering programs. They are also fast, simple, non-invasive, and expose the subject to a level of x-rays lower than that of a cross-country flight. DEXA exams provide both total body and up to 14 regional (trunk, individual arms & legs, android, gynoid, etc) results.
Body Composition is also estimated using cross-sectional imaging methods like magnetic resonance imaging (MRI) and computed tomography (CT). Since MRI and CT give the most precise body composition measures to-date, many pharmaceutical companies are very interested in this new procedure to estimate body composition measures before and after drug therapy especially in drugs that might change body composition.
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