Fat mass refers to the total amount of fat tissue in the body. It includes both essential fat, which is necessary for normal bodily functions, and storage fat, which serves as an energy reserve. Measuring fat mass helps assess overall health and can indicate risks for various conditions, such as obesity and heart disease. Body composition analysis often distinguishes fat mass from lean mass, which includes muscles, bones, and organs. Tools like bioelectrical impedance analysis and dual-energy X-ray absorptiometry (DEXA) are commonly used to measure fat mass. Understanding fat mass can guide individuals in making informed health and fitness decisions.