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Body Fat / Body Composition Tests
    

Brian Bambl B.S. Exercise Science 2011-05-26

There are multiple ways to have your body fat percentage tested, but the cost and accuracy varies greatly among the different methods.  Also, not all body fat methods are easily available in all areas.  Below is a list of the various types of body fat tests, the accuracy of each type of test, the estimated costs of having each test performed, and the cost of the equipment necessary to perform the tests. 

Body Fat chart

Dual Energy X-ray Absorptiometry (DEXA)

DEXA is one of the most accurate methods of testing your body fat percentage. It has an accuracy of + or - 1%.  This means if your body fat is tested using the DEXA machine and the results state that your body fat % is 15% then your body fat is between 15 to 16%.  However, DEXA is the most expensive method for testing your body fat and is generally only found at hospitals and major universities.  In addition to testing your body fat percentage the DEXA machine also tests your bone mineral density which is helpful for identifying osteoporosis and if you’re at risk for potential bone fractures.  The DEXA machine works by passing two beams of different energy levels through your body.  The machine then measures the amount of energy that your body absorbs and based on this energy it determines your bone density and your body fat percentage.

Dexa body fat testing

 

Bod Pod

The Bod Pod is probably the best method for testing your body fat percentage on the basis of price, ease of testing, and accuracy.  It has an accuracy of + or – 2 to 3%, the process is very easy, and the cost is often quite reasonable.  Bod pods aren’t available everywhere, but can be found at many colleges and large gyms.  The Bod Pod works on the principle of plethysmography or air displacement.  Basically the Bod Pod measures how much air your body displaces.  By measuring your body weight and then checking your body volume in the Bod Pod it is then possible to calculate your body density.  Then using a formula that is specific to your age, gender, and ethnicity it is then possible to accurately calculate your body fat percentage.

Bod pod bod fat testing

Hydrostatic weighing

Hydrostatic weighing is one of the most accurate methods of testing your body fat %.  It has an accuracy of + or - 2 to 3%.  Hydrostatic weighing works on the principle that muscle (1.10 g/mL), fat (.90 g/mL), and water (1.00 g/mL) all have different densities.  Due to this difference in densities fat floats in water and muscle sinks.  This difference in density causes you to weigh a different amount in water versus out of water.  By testing your weight out of water and in water makes it possible to calculate your body density and in turn calculate your body fat percentage. 

hydrostatic tank picture body fat testing

Bioelectrical Impedance Analysis

There are many types of bioelectrical impedance analysis machines.  However, they all operate on the same principle.  Bioelectrical analysis works on the principle that difference materials provide differing amounts of resistance to electrical currents.  In the case of your body’s “materials” we’re looking at how well muscle and fat resist a current.  Muscle is a far better conductor of electricity because it is largely made up of water while fat isn’t a very good conductor. Muscle is about 70% water by weight.  So the more that your body conducts the electrical current the more muscle that you have and the lower your body fat percentage is.  The electrical current that these machines send through your body is harmless and can’t even be felt.  The accuracy of these machines varies from model to model.  However, in general bioelectrical impedance analysis is accurate to about + or – 3 to 5%.

Generally speaking there are three different types of bioelectrical impedance analysis machines.  There is the basic handheld model, the combination model which includes a hand placement and a standing platform, and the most common standing platform model.

Handheld Bioelectrical Impedance Analysis (BIA)

Handheld Bioelectrical Impedance analysis picture

Standing/Handheld combo Bioelectrical Impedance Analysis (BIA)

Tanita 418

Standing Bioelectrical Impedance Analysis (BIA)

TANITA BF 680

Skin fold method using Calipers

Skin fold testing is one of the cheapest methods of body fat testing.  However, it requires a lot of experience and accuracy on the part of the tester.  Skin fold testing works on the basis that your body distributes fat according to patterns that are specific to age, gender, and ethnicity.  One of the assumptions is that 50% of your fat is subcutaneous fat or lies underneath your skin.  So during skin fold testing three to seven skin folds or “pinches” are taken on your body depending on the formula being used. These measurements are then taken and entered into a formula that is specific to your age, gender, and ethnicity and your body fat percentage is calculated.  Skin fold testing accuracy is + or – 3 to 5%.

Calipers

Body circumference measurements

Body circumference measurements or anthropometric measurements testing takes body girth measurements such as the circumference of your arm, waist, calf, and thigh.  These measurements are then entered into a formula to calculate your body fat percentage.  The accuracy of this type of test is + or - 3 to 8%.  It works on the basis that your body distributes fat according to specific patterns.  There is still much more research needed in order to make these tests more accurate. 

Near Infrared Interactance

The near infrared interactance test uses a beam of light and measures the amount of light that is reflected by your fat.  Based on the amount of light reflected helps determine your body fat percentage. This test has a wide range of accuracy of + or – 4 to 10%.

Futrex 52

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