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What Is the Best Way to Measure Body Fat?

Jun 27, 2011 | By Chance Woods
What Is the Best Way to Measure Body Fat?
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Excess body fat is a risk factor for a number of life-threatening diseases including heart disease, diabetes and cancer. It is also a limiting factor for performance in most sports. The best way to measure body fat depends upon your needs and resources. Some tests are highly accurate but expensive and inconvenient while other tests are very convenient and inexpensive but less accurate.

Most Accurate: MRI

Physical therapists, doctors and researchers have often used hydrostatic weighing and dual-energy X-ray absorptiometry as the standards for accuracy in measuring body fat. However, a study published in the November 1998 issue of "Journal of Applied Physiology" demonstrated that the MRI can more accurately calculate both internal fat deposits as well as visceral adipose tissue when compared to evaluations done by whole body composition tests done on cadavers. Although these tests are arguably the most accurate, MRI is quite expensive and the level of accuracy that it provides may not outweigh the prohibitive cost of the test for most people. Hydrostatic weighing and dual-energy X-ray absorptiometry are slightly less expensive options that provide nearly the same accuracy.

Least Expensive: Skinfold

Personal trainers and athletic trainers favor the skinfold test for accurate and inexpensive body fat measurements that can be done almost anywhere -- from the gym to the playing field to the client's home. Using relatively inexpensive calipers and charts created from linear regression formulas, trainers measure the thickness of skinfolds from three to six sites on your body including the back of your upper arm, your shoulder blade, your abdomen and your upper thigh. The skinfold test can be very close in accuracy to hydrostatic weighing, but with inexperienced personnel administering the test it can be wildly inaccurate. Dependence upon clinician proficiency is the main drawback to skinfold testing.

Least Invasive: Air Displacement Plethysmography

For individuals who are uncomfortable with removing their clothing in front of the test administrator, air displacement methods may be preferable. Instead of being submerged in a pool of water or exposing your skin for the administrator to pinch with calipers, you simply sit inside an airtight chamber, clothed in a modest bathing suit while the machine measures the air you are displacing. Air displacement test results can vary based on differences as miniscule as excess body hair, so they are not as reliable as MRI tests or hydrostatic weighing, but they are a relatively low cost option, with each test ranging from $60 to $150.

Most Convenient: Bioelectrical Impedance

In recent years, bioelectrical impedance scales and handheld devices have become widely available. The body fat scales you see in your local department store work on this technology. By standing barefoot on the scale, you allow the sensors to send a very mild electric current -- that you cannot feel at all -- up one leg, through your body and down the other leg. Based on the amount of time that the current takes to pass through your body compared with your weight, the scale is able to estimate the amount of body fat you have. Although these are arguably the most convenient body fat tests, they are very dependent on variables such as hydration. If you have slightly more or less water in your body than normal, the test results are likely to be inaccurate by several percentage points. You can minimize the inaccuracy of bioelectrical impedance by performing repeated tests under similar circumstances. For instance, testing every morning before breakfast.

References

Article reviewed by Jason Dean Last updated on: Jun 27, 2011

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