About Measuring Body Composition

Body composition refers primarily to the distribution of muscle and fat in the body, and its measurement plays an important role in both sports and health. Excess body fat may lead to obesity and increases the risk of getting many diseases. In sports, excess fat hinders performance as it does not contribute to muscular force production, and it is additional weight that requires energy to move about.

Body composition is often represented as a two compartment system; lean body weight and fat weight. The fat weight is then expressed as a percentage of total body weight, where percent body fat = (fat weight / total body weight) x 100.

Whatever method you use for measuring body composition will depend on what you wish to achieve, your desired accuracy level, your budget and time allocation.

General Body Composition

There are a few general methods for getting an estimate of body size and composition. These test are based on body dimensions, such as Body Mass Index (BMI) and Ponderal Index which use measures of height and weight. The Waist to Hip Ratio uses only girth measurements. These methods are commonly used large scale studies population studies or when a quick and simple measure is required.

Body Fat Measurement

world's fattest womanThere are quite a few different methods for measuring body composition, and they differ in accuracy, ease of measurement and expense. The page on body composition tests list the full range of methods.

There are formulas using skinfold measurements and a simpler method using formulas based on girth measurements. The equation of Yuhasz and Parillo use skinfold measures to estimate %bodyfat, while the formula of Jackson & Pollock , Sloan and Durnin and Womersley also use various skinfold measurements for equations to estimate body density, which can be converted to %bodyfat using the Siri Equation. Body density can also be estimated using Underwater Weighing and the Whole-body Air-Displacement Plethysmography (BodPod) method.

There are other more sophisticated equipment for measuring body fat levels, such as Bioelectric Impedance and Dual-Energy X-Ray Absorptiometry (DEXA).

Muscle Mass Measurement

It is not always the body fat that is of interest. There are several methods to measure the amount of muscle mass or lean body tissue. There is a simple equation for estimating the body muscle mass. There are also methods requiring sophisticated and expensive equipment and are not routinely available for most people. Such methods include DEXA, CAT and MRI scans to get accurate measurements of the composition of body tissue and TBK which can accurately determine the body's total cell mass. See more about measuring muscle mass.

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