Does anyone know what the difference is in how bodyfat % is calculated using scales that have both an "Athlete" and "Normal" setting? I have both a Tanita scale with bodyfat%, and an Omron handheld bodyfat analyzer, and I get wildly different results based on what mode they are in.

The Tanita instructions say if your resting heart rate is around 60, use Athlete. The Omron gives you a formula based on activity duration, frequency, and intensity. (P90X certainly qualifies for athlete mode here!).

Why the two different modes, and how do they calculate % differently?

Thanks.

There are many, many different formulas for calculating body fat. Some take into consideration ethnicity and other such factors. Body fat scales use an electronic signal by sending a small current through your body and measuring resistance. By giving you the choice of whether to use one mode or the other, you are narrowing down the formula for the scale and based on your inputs(height, sex, age, athletic or regular), it decides which algorithm to use to calculate your BF%.

With all that being said, I have found that electronic scales are HORRIBLE at body fat measurement. According to my scale, I am at 26% BF. According to my calipers, I am around 13-14% (last time I checked). And when I use a tape measure and input my numbers onto online calculators, it comes up with 13.80.

By the way, Accumeasure calipers are regarded as the best way to approximate BF %.