Different methods of body composition assessment allow for the direct or calculated measurement of the mass of different types of body components, such as fat, bone, water, lean mass, etc. Whole-body assessments of body composition differ according to the number of components, or “compartments,” into which the total body mass is divided. There are three main models of body composition:[1]
- A 4-compartment model divides the body’s mass into total body water, bone mineral content, fat mass, and fat-free mass.
- A 3-compartment model (e.g., DXA-DEXA|dual-energy X-ray absorptiometry) divides the body’s mass into bone mineral content, fat mass, and fat-free mass.
- A 2-compartment model (e.g., hydrodensitometry or underwater weighing, air displacement plethysmography, bioelectrical impedance analysis) divides the body’s mass into fat mass and fat-free mass.
The 4-compartment model is considered the gold standard, but it requires a variety of equipment and is costly and time-consuming, so it’s not commonly used.