How is "body composition" defined?

Body composition refers specifically to the proportion of fat mass relative to lean mass in an individual's body. Lean mass encompasses muscles, bones, organs, and water, while fat mass includes all body fat. This measure is important because it provides a more accurate representation of an individual's health and fitness than weight alone. For example, two people may weigh the same but have different body compositions—one may have a higher percentage of fat mass, while the other has a higher percentage of lean mass, which can influence their overall health and performance in physical activities.

Understanding body composition helps in assessing physical fitness and health risks, guiding nutrition, and creating exercise programs tailored to individual needs. This nuanced view goes beyond just looking at total weight or strength, which do not give a complete picture of one's health and fitness.