Lean Body Mass Calculator
Lean Body Mass (LBM): Definition and Importance
Lean Body Mass (LBM) refers to the portion of body composition that excludes fat. It comprises the weight of bones, muscles, blood, skin, organs, and other non-fat tissues. On average, LBM makes up 60–90% of total body weight, with men typically having a higher proportion than women.
LBM is particularly important in medical settings, where it helps determine dosages for certain anesthetic agents (especially water-soluble drugs) and is used in diagnostic tests. However, for general fitness and health tracking, body fat percentage is more commonly monitored than LBM.
Lean Body Mass Formulas for Adults
Several equations estimate LBM (eLBM). Below are the most widely used formulas, where:
- W = weight (kg)
- H = height (cm)
The Boer Formula (1984)
- Males: eLBM = 0.407W + 0.267H – 19.2
- Females: eLBM = 0.252W + 0.473H – 48.3
The James Formula (1976)
- Males: eLBM = 1.1W – 128(W/H)²
- Females: eLBM = 1.07W – 148(W/H)²
The Hume Formula (1966)
- Males: eLBM = 0.32810W + 0.33929H – 29.5336
- Females: eLBM = 0.29569W + 0.41813H – 43.2933
Lean Body Mass Formula for Children
The Peters Formula (2011) estimates LBM in children (≤14 years) based on extracellular volume (eECV):
- eECV = 0.0215 × W^0.6469 × H^0.7236
- eLBM = 3.8 × eECV
Lean Body Mass vs. Fat-Free Mass
Though often used interchangeably, LBM and Fat-Free Mass (FFM) differ slightly:
- LBM includes essential fat (found in organs, bone marrow, and nerves).
- FFM excludes all fat, including essential fat.
The difference between the two is typically 2–3% in men and 5–12% in women, as women naturally store more essential fat.
References
- Boer (1984) – Am J Physiol
- James (1976) – DHSS/MRC Report
- Hume (1966) – J Clin Pathol
- Peters et al. (2011) – Br J Anaesth
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