Making BIA Work for You

Making BIA Work for You

Bioelectrical Impedance Analysis (BIA) is a method of body composition assessment that applies a weak, imperceptible electrical current to the body, and then measures the resistance of that current. Water is a good conductor of an electrical current and, since there are differences in the water content of fat mass vs lean mass, these tissues can be distinguished from one another by their resistance differences. However, this technique is also subject to significant error. BIA relies heavily on the assumption that the water content of the body can be accurately measured and that water is a known and constant percentage of fat free mass. So, to minimize this major source of error, specific protocols or guidelines are necessary to minimize errors.

We have listed below several ‘pre-test’ guidelines that should be followed to obtain the most accurate measurement. These guidelines are shown in the box below and will help to ensure that hydration is normal and help reduce its day to day variability. Beyond following these guidelines, what other ways are there to make BIA work for you?

Choose the best BIA method. There are accuracy differences between devices whether or not they are made by the same manufacturers. Devices range from supine to standing, single vs multiple frequencies, and regional vs whole body. Do your research and look for validation studies on devices that show small errors.

Make sure you standardize the measurement methods you use. For example, for every test, follow the recommended guidelines and do not test someone who has not prepared properly for the test. This is especially important if you are limited on which BIA device you have available.

If you are following changes over time, make sure you document and replicate the conditions under which measurements are made. Make a note of the time of day, the temperature of the room, the manner in which the client prepared, the date of the last menstrual cycle for women, etc, so that these can be replicated for follow-up measurements.

Make sure to report results with their range of error (from those validation studies).This will allow clients to understand that there is no method without error. Clients can also begin to understand why very frequent body composition measurements are not recommended.

Consider performing duplicate measurements on different days. By using the average of duplicate measurements, you can increase your ability to detect changes over time. Be sure to measure on different days within a short period of time and to exactly replicate your measurement methods.

Following the pre-test guidelines and implementing the strategies above will improve the usefulness of BIA in your practice.

For help sifting through the many BIA devices and equations, consider taking the Level 1 Body Composition Certification Course that we offer!

Procedural Guidelines

Your client should prepare in the following ways prior to having a BIA test:

• No eating or drinking within 4 hours of the test
• Abstain from alcohol for 12 hours before the test
• No exercise within 8 hours of the test
• Void (urinate) within 30 minutes of the test
• No diuretics (if possible)
• Postpone test if the client reports water retention (such as with menstrual cycle, etc)