Assessing body composition means measuring the different components that make up the body.

This measurement is carried out at the molecular level by bioimpedancemetry which manages to divide the different "compartments" of the human body by differentiating the fat mass from the lean mass, and subdividing the composition of the lean mass even more specifically.

A body composition that tends to be rich in adipose tissue and poor in muscle mass is correlated to poor overall fitness (cardio-circulatory, respiratory, muscular, articular, etc.), to poor athletic-sports ability and to a greater physical risk linked to ominous events such as hypertension, diabetes, obesity, dyslipidemia, metabolic syndrome, cardio-vascular complications and joint pathologies.

It is possible to measure the subject's weight, BMI, fat mass (FM), lean mass (FFM), percentage of total body water (TBW), the fraction of intracellular water (ICW) and extra-cellular ( ECW).