How is fat mass defined ?

The fat mass represents 25% to 35% of the body mass. It can be measured according to a special pair of scales – the impedance meter. The body mass index (BMI) can also be calculated. The BMI can be used to measure the excess weight of a person by taking into account the person’s weight and size.
This is found through the measurement of weight in kilos, divided by height in meters squared [(Weight (kg)/Height (m²)]. It is a reliable method for adults from the age of 20 to 65, but it cannot be used for pregnant women, or for those that are breast feeding, neither can it be used for athletes involved in sports requiring stamina, nor for very muscular people. The BMI is considered to be normal when it is between 18,5 and 24,9.