Body Composition Estimation

It is extremely difficult to determine body composition, with accuracy, by weighing a person or by looking at him or her. There are many"thin"people who have lost so much lean mass that they actually have a relatively high body fat percentage, and there are also many "large"people who are actually relatively lean. Even with modern equipment and sophisticated equations it is extremely difficult to accurately measure body fat percentage and to consistently repeat that measure. We have no direct means of assessing body composition (the subject wouldn't survive if we tried), so all the techniques available to us are attempting to accurately estimate the fat mass or the fat-free mass. Each technique uses a different means of making this estimate, so cross-comparisons between techniques should not be made. As an example, athletes who have had body fat percentage estimated via skinfolds should not compare the values from that method with values obtained by bioelectrical impedance analysis. The values obtained from these techniques are likely to be sufficiently different that, at the very least, the athlete will be confused. The common methods for assessing body composition include

• hydrostatic weighing (underwater weighing),
• skinfold measurements applied to prediction equations,
• bioelectrical impedance analysis (BIA), and
• dual-energy X-ray absorptiometry (DEXA).

Hydrostatic Weighing (Hydrodensitometry)

Skinfolds

Bioelectrical Impedance Analysis (BIA)

Dual-Energy X-Ray Absorptiometry (DEXA)