Fat-free body mass: the other component (to body fat) of body weight, including musculoskeletal elements often associated with health and fitness. For example, some athletes with a large amount of muscle may be "overweight" according to weight charts, or even weight for height charts, such as the BMI, but much of the "excess" weight is in the form of fat-free musculoskeletal tissue. Therefore, they would not be considered "overfat" or "obese". Extremely overweight individuals have an excess of both fat-free and fat body mass, but it is the latter that imparts health risks.