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RECOMMENDATIONS The American Council on Exercise {Link without Title} has associated categories with ranges of body fat. Women generally have less muscle mass than men and therefore they have a higher body fat percentage range for each category. MEASUREMENT TECHNIQUES Body average density measurement The most accurate method has been to weigh a person underwater in order to obtain the average density (mass per unit volume). Since fat tissue has a lower density than muscles and bones, it is possible to estimate the fat content. This estimate is distorted by the fact that muscles and bones have different densities: for a person with a more-than-average amount of bone tissue, the estimate will be too low. However, this method gives highly reproducible results for individual persons (+/- 1%), unlike the methods discussed below, which can have an error up to +/-10%. {Link without Title} The body fat percentage is commonly calculated from one of two formulas:
In these formulas, ρ is the body density in kg/L. For a more accurate measurement, the amount of bone tissue must be estimated with a separate procedure. In either case, the body density must be measured with a high accuracy. An error of just 0.2% (e.g. 150 mL of trapped air in the lungs) would make 1% difference in the body fat percentage. The body density is measured by weighing a person underwater, with all air expelled from the lungs. This procedure is normally carried out in laboratories with special equipment. However, it is possible to make an estimation without assistance in a swimming pool. A person who neither floats nor sinks with empty lungs in a swimming pool would have a density of 1 kg/dm3 and an estimated body fat percentage of 43% (Brozek) or 45% (Siri), which would be extremely obese. Persons with a lower body fat percentage would need to hold some kind of floatation device, such as an empty bottle, in order to prevent them from sinking. If the floatation device has mass ''m'' and volume ''v'', and the person has a mass ''M'', then his or her density is : where is the density of water kg/L at 22 °C (72 °F) . For example, a person weighing 80 kg needs to hold a floater with a volume of 4.5 L and a mass of 0.5 kg has a density of 1.05 kg/L and hence a body fat percentage of 21%. Note that both the Brozek and Siri formulas are claimed to give systematically too high body fat percentages. [http://mb-soft.com/public2/bodyfwp2.html] Skinfold test A simpler test for measuring body fat is the ''skinfold test'', in which a pinch of skin is precisely measured by calipers at standardized points on the body to determine the thickness of the Subcutaneous fat layer, and converted to body fat percentage by an equation. Bioelectrical impedance analysis This method can be conducted very accurately in the laboratory or at home with a less accurate, though affordable, home scale. From weight and waist Less accurate again, but most readily available (e.g. on the internet), are formulae which calculate a percentage from weight, waist measurement and sometimes other measurements. These are widely available on the internet and elsewhere. EXTERNAL LINKS
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