Recently, people have begun to realize that measuring body composition is a more reliable way of assessing health than using BMI. Even the New York Times has published articles highlighting the inaccuracies of BMI. As a result, body composition analysis has gained popularity, and one of the most popular tools for analyzing body composition is a device that uses bioelectrical impedance analysis (BIA).
BIA devices are becoming increasingly popular due to their speed, convenience, and accuracy in measuring body fat percentage and body composition. These devices come in a range of prices, with some as low as $50, and others costing tens of thousands of dollars. But what is the difference between them?
Fundamentally, all BIA devices use the same method: a small, safe electric current is sent through a person's body, and the resistance caused by the variation in water content in different parts of the body, such as fat and muscle, is measured. This information is then analyzed and translated into useful outputs, such as body fat percentage and lean body mass.
However, not all BIA devices are created equal. Here are some things to consider when purchasing a BIA device to measure body composition:
1. Check the Frequencies
All BIA devices use at least one electric current set at a specific frequency to measure body composition. In the past, this frequency was traditionally set at 50 kHz, and some devices continue to use this single frequency. Worse still, as BIA devices become more and more prevalent in home use, most four-electrode body fat scales only use a current frequency of 5kHz. However, research from the early 1990s suggested that single frequency devices set at 50 kHz did not accurately predict changes in total body water. Instead, the use of multiple frequencies was found to be more accurate. Lower frequencies are better suited for measuring extracellular water, while higher frequencies are better suited for measuring intracellular and extracellular water. Therefore, a device that uses at least two frequencies, one on the lower end and the other on the higher end, is ideal.
2. Understand What Is and Isn't Measured
Many BIA devices are designed to measure impedance for a specific section of the body and then use those results to estimate the remaining sections. It is important to understand what exactly your BIA device is measuring and estimating before choosing one. 4-electrode scales only measure impedance for the legs and make assumptions about the composition of the upper body based on the legs' composition. Handheld BIA devices measure impedance in the arms and upper body and estimate the lower half of the body based on the upper body's results. On the other hand, Direct Segmental Multifrequency-BIA (DSM-BIA) technology analyzes the body in five distinct sections, including the two arms, two legs, and torso. DSM-BIA devices analyze each section independently and produce a measurement for the entire body based on direct measurements, similar to how DEXA machines operate. DSM-BIA technology has been found to be accurate when compared to DEXA results and offers results based on direct measurements, without using estimations to compensate for unmeasured areas.
3. See What Outputs It Provides
BIA devices range in their capabilities and the outputs they are able to produce. While all BIA devices will measure body fat percentage, some devices can provide more comprehensive outputs. For instance, Skeletal Muscle Mass is the muscle that you can grow and develop through exercise and proper nutrition, and tracking it can help ensure that your muscle gains are due to muscle, not water. Body water analysis can provide information about whether or not your body water levels are balanced. Additionally, Segmental analysis can provide insight into which specific parts of your body may require more muscle development or fat loss. By analyzing each segment of the body separately, it can also indicate whether the distribution of fat and muscle mass is well-balanced or not.
Purchasing a BIA device can be a helpful way to measure body composition, but it's important to choose the right one for your needs. Checking the frequencies and seeing what outputs the device provides can help you choose the device that is most accurate and useful for you.