How does a body composition analyzer determine body composition?

We examined how a body composition analyzer determines body composition. Using measured body weight and the bioelectrical impedance value, the analyzer estimates body fat composition as a stastically confirmed value based on age, gender and height. By comparing two subjects of the same age, gender and body weight, the taller has a smaller body fat component, and a larger impedance value corresponds to a larger fat component. The fat component does not depend on age, but the visceral fat area is estimated to be higher for a male over 40 years old than for a female or a younger person.