Posts Tagged 'impedance'

What is BFA / Body-Fat-Analysis?

The term “BFA” (body-fat-analysis) has become a frequently used term in the past few years in health and fitness media, especially in product advertisements and fitness magazine articles.

BFA  is a method used to determine the amount of body fat as expressed by a percentage of body weight.   There are actually 6 methods used to identify a person’s percentage of body fat relative to their weight:

  • Bioelectric impedance
  • “Bod pod” (air displacement)
  • Dual energy x-ray absorptiometry (DEXA)
  • Near infrared interactive (NIR)
  • Skinfold caliper measurements
  • Underwater weighing (hydrostatic weighing) 

Of the 6 methods, two that are widely used (and most likely familiar to readers) are bioelectric impedance and hydrostatic weighing (“dunk tank”). 

The hydrostatic method is widely regarded as the most accurate and is used increasingly as a measuring method in bariatric surgery and weight loss clinics, as rates of obesity continue to trend upward statistically among the U.S. population.  The subject is immersed completely in a tank, and the displaced amount of water is measured, representing body mass.  A formula is then applied to the amount of displaced water to determine  body fat composition.

Bioelectric impedance is a much simpler method and inexpensive, and therefore widely used in consumer health-monitoring devices, including weight scales:  Simply expressed, a very small electric current generated by consumer batteries enters one leg from the base of the scale, passes across the abdominal area, down the other leg and re-enters the scale.  The resistance the electric current encounters is measured and quantified by the scale electronically, and a numerical value is displayed that represents amount of body fat. 

However, there are significant accuracy problems associated with the bioelectric impedance method of determining body fat composition, which will be discussed in another article.