Lean body mass (LBM) is a measure of the mass of the body excluding fat. It is an important measure of body composition as it is a more accurate indicator of health and fitness than total body weight.
Various methods exist to calculate LBM, including the use of calipers, underwater weighing, and bioelectrical impedance analysis. For example, the widely known formula developed by James B. Deurenberg developed in 1991 estimates LBM using height, weight, age, and gender.