Body Composition: Bioelectrical Impedance Analysis

Someone looking to lose body fat will need a way of tracking their progress. Although total body weight can sometimes indicate the loss of body fat, it is not a reliable source. There are numerous ways to measure body composition, one of which is the Bioelectrical Impedance Analysis (BIA). But what is it and how does it work?

This technique uses a model that breaks down the total body mass into two compartments: fat mass and fat-free mass.1,2 The two-compartment model has gained popularity recently because of the association of excess body fat and the increased risk of cardiovascular diseases.1

In this model, the body is broken down into body fat, and all other remaining tissue.1,2 Therefore, any technique using the two-compartment model will attempt to separate the fat mass from the fat-free mass. BIA does just that.

After determining the fat-free mass of a subject, then the body fat is simply the the total body weight minus the fat-free mass.1 This is the beauty of the two-compartment model. There are assumed known and constant proportions of water, protein, and minerals within humans for fat-free mass which allows many BIA machines to obtain accurate results.2

BIA measures impedance of a small electrical current, so small you cannot feel it, as it travels through the body.2 Body fat acts as an electrical insulator, so higher fat percentages will reduce the amount of electricity that will complete the circuit through the body.

Source: http://www.jawon.com/reng/res/principles-of-bioelectrical-impedance-analysis.html

As the current flows through the body, it is able to travel through certain tissues that are conductors, such as muscle and fluids, more easily than tissues that are insulators, such as fat and bones.2 With other factors such as age, height, gender, and weight, bone mass can be calculated and be taken into consideration to the amount of impedance that is in the body.

Two common instruments, images below, are inexpensive, portable, quick and easy to use, and have passive subject participation.2 Both instruments can fit into any budget and can even be used frequently at home. Both items are similar, but the first instrument needs a manual submission of weight whereas the second has a scale attached to the system. Someone looking for a way of tracking body composition and fat loss can purchase a relatively inexpensive and quick to use Bioelectrical Impedance Analysis machine.

Source: http://www.weightlosstriumph.com/omron-hbf-306cn-fat-loss-monitor-review.html
Source: http://www.bodyhack.com/blog/5-ways-to-measure-body-fat-composition-1433

Sources

1Ellis, K. (2000). Human Body Composition: In Vivo Methods. Physiological Reviews, 80(2), 649-680. Retrieved from http://physrev.physiology.org/content/80/2/649.short#sec-15

2Lee, S. Y., & Gallagher, D. (2008). Assessment methods in human body composition. Current opinion in clinical nutrition and metabolic care, 11(5), 566.