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Ways to Measure Body Fat Percentage

Measuring body fat is the best way to determine weight loss success.
Measuring body fat is the best way to determine weight loss success.
(AP Photo/Frank Franklin II)

It’s easy to get caught up in measuring appropriate body composition based on one’s weight. Height to weight ratios have been around for years, many doctors still use them, and most people are comfortable with determining how much they should weigh based on these scales. The problem with height to weight ratios is they aren’t very accurate. The scale in general is a pretty poor way to determine appropriate weight, as it does not differentiate between lean body mass (muscle and bones) and fat mass. To get a proper reading on your body composition you must measure your body fat percentage.
Long considered the “gold standard” of body fat analysis due to its accuracy (repeated studies show a variation of 1.5 percent according to Georgia State University), hydrostatic weighing is based on Archimedes’s Principle, which according to NASA states that the buoyant force on a submerged object is equal to the weight of the fluid that is displaced by the object. This means that the greater the fat percentage, the more buoyant a person will be due to the density difference in muscle and fat.
Skin calipers are the most commonly used form of body fat measurement due to the fact that it is easy to perform, takes very little time, is inexpensive and is relatively accurate (plus or minus 3 percent according to Georgia State University). The calipers assume that the subcutaneous fat (fat directly below the skin) is consistent throughout the body, which is the biggest reason for the variance.
Another relatively common way to measure body fat percentage is called Bioelectrical Impedance Analysis (BIA). BIA works by sending a low voltage electrical current through the body and measures the time it takes for the signal to return to the source. Because fat is a poor conductor of electricity, the longer the time takes, the higher ones body fat percentage. BIA has a plus or minus 3 percent accuracy rate, however, this depends the subject fasting for at least 4 hours prior to the test, not exercising for at least 12 hours before the test, urinating prior to the test, and not drinking alcohol or taking diuretics for up to 48 hours before the test is done.