There are many ways to measure body composition. Underwater weighing, skinfold measurements, and bioelectrical impedance are just some of the methods used by the health and fitness industry. If you are interested in having your body fat measured, remember that these methods have a degree of inaccuracy and should not be looked at as proof that you are healthy or unhealthy. Distribution of body fat varies depending on genetics, exercise and eating habits.

Skin fold measurement This method of determining body composition is popular because it is inexpensive and is assumed to be reasonably accurate. It is based on the belief that substantial fat is proportional to overall body fat and that by measuring in several places, total body fat can be calculated. (The assumption is that fifty percent of body fat is located just under the skin and the remaining fifty percent is found elsewhere.) During this test, a metal or plastic caliper is used to measure skin fold thickness at various sites on your body. The tester must be able to properly identify a site measurement and then pinch the skin gathering only fat and no other tissue. The sum of the measurements is applied to one of many pre-determined "norms" for gender and age. (Do not use this method after exercising, as the transfer of fluid to the skin can result in overestimations.) What you need to know: Your "number", or percent body fat from this method depends on many things, including age, gender, the experience of the tester, and how many sites are used. There are currently over 100 different equations available to estimate body fat with the use of skin fold calipers, a reflection of the problem of accuracy of this method. Because of this, many organizations, including the U.S. Army and the Los Angeles Police Department have abandoned the use of them.

Body Mass Index Another way to estimate body composition is the Body Mass Index or BMI. This is the ratio between your height and weight and is calculated by dividing your weight in kilograms by your height in meters squared. Since only height and weight are used, no indication of actual leanness or fatness is determined by this method. It is better to use BMI as a predictor of determining when extra pounds may translate into health risks. If your BMI is high, you may have an increased risk of developing hypertension, cardiovascular disease, adult-onset diabetes and other conditions. There are individuals for whom the BMI is not appropriate. Competitive athletes and bodybuilders, for example, will have a higher BMI due to a relatively larger amount of muscle. Women who are pregnant, growing children or sedentary elderly individuals are not good candidates for this type of measurement. What you need to know: In June 1998, the federal government announced guidelines which create a new definition of what is considered a "healthy weight"-a BMI of 24 or less. So now a BMI of 25 to 29.9 is considered overweight. Individuals who have a BMI of 25 to 34.9, and have a waist size of over 40 inches for men and 35 inches for women, are considered to be at especially high risk for health problems. A BMI of 30 and over is considered obese and increases the risk of death from any cause by 50 to 150 percent, according to some estimates.

For example, two people have the identical skinfold measurement. The measurements will be summed and applied to one of the many equations available. If you are female, your reading will automatically be higher, if you are older, the same is true. I realize that these tests must use some data by which to calculate readings, but I think that because each of us is so unique, the accuracy of most body fat methods suffers greatly. We know that strength training increases bone density and lean muscle tissue, as well as reduces body fat, yet the person being tested is never asked about such habits.

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