An electrical signal is introduced and an impedance value is obtained. This is then entered into an equation to predict percent body fat. Foot Pad Model. The person stands in bare feet on the machine. Computer software in the product measures impedance and then uses this and the person's gender, height, fitness level, weight, and, in some cases, age to determine body fat percentage.
First weight appears on the machine and then percent body fat appears.
In both home and professional uses, people need to be adequately hydrated. This is because this method assumes that the body is within normal ranges for its water content. Changes in a person's hydration levels can be due to failure to drink enough water, hormonal changes, food, caffeine or alcohol consumption, strenuous exercise, stress or illness, or taking prescription drugs. If a person is dehydrated, the amount of fat will likely be overestimated. Some, but not all Bioelectrical Impedance systems, are simple and fast.