Body Fat Testing through Bioelectrical Impedance (BIA)

In addition to the bathroom scale, how our clothes fit, and how we feel day to day, body fat measurements provide us with a bit more information about where we stand with our health and fitness goals. Simply put, getting your body composition estimated provides information about how much of your body is fat and not fat (muscle, bone and organs). You are likely aware that too much body fat is a reason for concern. Carrying too much fat (especially around the middle) increases the chance of developing conditions such as type 2 diabetes, heart disease, hypertension, and joint disease.

Bioelectrical Impedance Analysis:

One method of estimating body fat is through bioelectrical impedance (BIA). It is a painless and easily accessible procedure that is safe for most individuals. Those with a pacemaker or women who are pregnant should avoid the test.

How does it work?

The test works by passing a low level imperceivable current through the body. The current moves faster through fat-free mass, due to its higher water content, than fat mass. The resistance that the current encounters is measured and then plugged into a mathematical equation to come up with total body water, fat-free mass, and body fat.

How accurate are the results?

BIA has a 3-4% chance of error under optimal testing conditions. Thus if your result indicates 30% body fat, this could mean you have 26-34% body fat. You can expect this same level of accuracy with other practical body composition testing procedures.

What are optimal testing conditions?

The test is highly dependent on hydration level at the time of the test. For the most accurate results, it is important to be perfectly hydrated. Thus, prior to the testing, you should be informed of a hydration protocol to follow. This may include avoiding exercise for 4 hours prior to the test, avoiding a meal for 3-4 hours prior to the test (water is ok), avoiding saunas, and abstaining from alcohol for 12 hours prior to the test. Make sure to ask the clinician who performs your test about the pre-testing requirements.


  • Generally inexpensive test.
  • Very quick. The test takes less than 1 minute to conduct. Yet discussing the results can take some time, depending on the questions you have and your health goals.
  • It is much more accessible to the general public. Of note, bioelectrical impedance is not as valid and reliable as hydrostatic or underwater weighing.
  • Operating a bioelectrical impedance machine doesn’t require formal training. This is quite different from skinfold caliper testing which requires that the skilled and competent clinician complete the test using high quality calipers and inputting the numbers into an appropriate equation.


  • Those who are pregnant or have a pacemaker should avoid BIA.
  • Hydration level greatly impacts the results.
  • Misinterpretation may occur. While anyone can operate the machinery, a qualified health professional is best to interpret the results.


Bioelectrical impedance analysis(BIA) is a quick and painless way to get a read on your body composition. It’s accuracy is on-par with other practical body composition techniques. If you have the chance to have this test done, I would recommend it!

Joanna Kriehn is a Registered Dietitian Nutritionist and Certified Diabetes Educator with a passion for supporting individuals as they move towards a healthier lifestyle.

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