Lean body mass

Human body weight
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Lean body mass (LBM), sometimes conflated with fat-free mass, is a component of body composition. Fat-free mass (FFM) is calculated by subtracting body fat weight from total body weight: total body weight is lean plus fat. In equations:

LBM = BW − BF

Lean body mass equals body weight minus body fat

LBM + BF = BW

Lean body mass plus body fat equals body weight

LBM differs from FFM in that cellular membranes are included in LBM although this is only a small percent difference in the body's mass (up to 3% in men and 5% in women)^[1]

^ Yu, S; Visvanathan, T; Field, J; Ward, LC; Chapman, I; Adams, R; Wittert, G; Visvanathan, R (14 October 2013). "Lean body mass: the development and validation of prediction equations in healthy adults". BMC Pharmacology & Toxicology. 14: 53. doi:10.1186/2050-6511-14-53. PMC 3833312. PMID 24499708. LBM differs from FFM in that lipid in cellular membranes are included in LBM but this accounts for only a small fraction of total body weight (up to 3% in men and 5% in women)