Post edited 3:38 pm – July 3, 2009 by Dr. Ray

Good question! Bioimpedance is a tool for assessing body fat by sending a painless electrical current through the body. Lean tissue contains a lot of water and therefore conducts the electical current with little resistance while adipose (fat) tissue has little water and thus does not conduct electricity. The machine, using sophisticated calculations, assesses how this current transmits through the body and determines how much fat, lean tissue and water you have in the body. That is the “what” and the “how” of bioimpedance, but the big questions are…

“Does it work?” and “Is it accurate”

Bioimpedance can certainly be used as one tool for assessing body fat, however, there are a few guidelines to follow for best result:

1. Buy a scale that uses electrodes in the hands and feet. Most bioimpedance scales only send a signal through the feet which will only assess lower body composition. This is not as useful and accurate, especially if you carry more fat on top or on bottom. I do use such a scale, the one that I have used is called the InnerScan Segmental Body Composition Monitor BC-568 by Tanita. This scale offers a lot more information than standard foot sensor based bioimpedance scales.
2. Have a glass of water approximately one hour prior to testing. This will make sure that you have enough water in the tissues to accurately assess body composition.
3. Try to test on an empty stomach. Food in the stomach could alter the results.
4. Void the bladder and bowels prior to testing when possible.
5. Try to test at the same time every day.
6. Do not exercise prior to testing.
7. Use bioimpedance to assess progress more than individual measurements. If the machine says that you are 20% body fat and a week later it shows 19% body fat and two weeks later 18% then we know that we are moving in the right direction.

Remember, you must approach these types of tools with a level of sophistication that prevents you from getting worked up by one or two rogue results. In my experience, these scales can overestimate the body fat a bit. This means that if you have a body fat of 17%, the scale may show 19-21%. This is why I focus more on how things change rather than the actual individual reading when using this scale as a tool for assessing progress.