Body composition was actually explored centuries ago by Archimedes, though most of the data on this subject has been completed in the four decades. There is very good research to support the idea that our bodies strive to be a certain percent body fat and though it is possible to drive it lower or let it go higher, if we exercise and eat right, our body fat will seek its own level. Nevertheless, the desire to know percentage of body fat still prevails.

If you are considering having your body fat measured, you should know that there is a certain degree of inaccuracy that can occur. It would be wonderful if we could simply go in and have our fat percentage measured, no questions asked. Unfortunately, this is not the case.

The tester needs to know many things about you, including how old you are, gender, height, and/or weight. Have you ever wondered why? This information is necessary because your body fat reading ultimately will be based on a pre-determined formula. The assumption is that no matter what, everyone loses muscle and bone density and gains body fat as they age, and that women are fatter than men.

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.

Body fat testing, if used on a repetitive basis, can indeed be used to provide you with a means to measure progress. Just remember to test yourself or get tested on a monthly basis, using the same method and the same technician. If you are exercising regularly and eating a balanced healthy diet, with or without body fat testing, you’ll experience a decline in the fat to lean ratio and move toward your goals. There are many tests available, today I will be discussing one of them.

Hydrostatic weighing

This method, also referred to as “underwater weighing,” is based on the assumption that density of lean tissue is greater than that of fat tissue. Therefore, lean tissue will sink in water and fat tissue will float.

By comparing a persons mass measured both under water and out of the water, body composition is calculated. You may have read that underwater weighing is the most accurate way to get a body fat measurement. However, this is not always the case. In order to get an “accurate” reading, you must be sure to empty your lungs by exhaling fully while having your entire body submerged in a tank of water for 10 to 15 seconds. You must stay there until a technician can get a reading. This procedure may be repeated 7 to 10 times. Total test procedures may require 45 minutes to one hour.

To find out more about the accuracy of hydrostatic weighing , consecutive tests with the same subject and the same technician have been done in a controlled setting, still there was a plus or minus of 2.5 %. It is important that the technician is experienced, as it can be difficult to read the scale accurately. In addition, hydrostatic weighing methods assume that the density of bone in humans is constant, which is not true. For example, trained athletes have higher bone density than a less active or elderly person. Thus, differences in bone density will create test errors.

What you need to know: Hydrostatic weighing is time-consuming, requires expensive equipment and therefore can be costly, and relies heavily on the expertise of the technician performing the test. In addition, fear of immersion, obesity and infirmity are barriers to the hydrostatic measurement of accurate body composition analysis.

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