Bioelectrical Impedance Analysis (BIA)
Perhaps two of the most familiar body fat percentage measures - Omron Monitor and Tanita Scales - are Bioelectrical Impedance Devices.
A small constant current is passed (at a fixed frequency) between electrodes. The device measures the flow of the current - impedance being low in lean tissue (where fluid & electrolytes are primarily contained) and high in fat tissue - and an impedance measure is reached. Using an assumed hydration fraction for lean tissue (muscle), an estimated lean body mass is then calculated. Thus, body fat (Bodyweight minus Lean Body Mass = estimated Body Fat) and relevant percentages reached.
Suitable for a
"ball park" body
fat percentage measure for Mr. and Mrs. Average, the Omron Monitor
and Tanita Scales are widely used in the fitness industry, as they require
no skill from the assessor, are un-intrusive and are easy fitness
tests to perform.
Unfortunately, as regards a more muscular individual,
rather than rely on the results of these body fat percentage measuring
devices, you'd be better off making an educated guess, as results will
typically indicate a far higher than accurate body
fat percentage. In fact, in instances of extreme leanness, such as
a pre-competition bodybuilder with a true measurement of around 5%, I
(GP) have known the Omron Monitor
and Tanita Scales provide estimated measures as high as 30% body fat.
That said, it's a source of constant amusement (sorry to certain individuals!)
that many men with positive body dysmorphia (the opposite of most women)
are aware of false highs with these types of body fat measure and believe
this to be true in their circumstance, which is clearly untrue to anyone
else. Naturally, they're disappointed when you advise them that the Tanita
Scale's right on this occasion.
Another note to mention, many leisure trainers will pop on Tanita Scales both before and after training - DO NOT! Your bodies lower fluid levels post-training will increase the impedance measurement and therefore result in an artificially high body fat percentage reading.
Above, I've pooh-poohed the most commonly used Bioelectrical Impedance measuring devices (Omron Monitor and Tanita Scales), but I've always found the Bodystat 1500 reliably accurate. Compared to the Omron Monitor and Tanita Scales, the Bodystat 1500 is more expensive, more intrusive, and more labour intensive, BUT, as mentioned, MORE ACCURATE. Something else to note, with a wide variety of subjects, I have always found that a correctly measured 4 Site Caliper Skinfold Measurement returns near identical results to the more expensive Bodystat 1500.
If pregnant or fitted with a pacemaker, you should not perform a Bioelectrical Impedance body composition test. You may also wish to refer to our pre-test precautions.
