Lean body mass (LBM), sometimes conflated with , is a component of body composition. Fat-free mass (FFM) is calculated by subtracting

body fat Adipose tissue (also known as body fat or simply fat) is a loose connective tissue composed mostly of adipocytes. It also contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, Blood vessel, vascular endothel ...

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)

Overview

The percentage of total body mass that is lean is usually not quoted – it would typically be 60–90%. Instead, the body fat percentage, which is the complement, is computed, and is typically 10–40%. The lean body mass (LBM) has been described as an index superior to total body weight for prescribing proper levels of medications and for assessing metabolic disorders, as body fat is less relevant for

metabolism Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the co ...

. LBW is used by anesthesiologists to dose certain medications. For example, due to the concern of postoperative opioid-induced ventilatory depression in the obese patient,

opioid Opioids are a class of Drug, drugs that derive from, or mimic, natural substances found in the Papaver somniferum, opium poppy plant. Opioids work on opioid receptors in the brain and other organs to produce a variety of morphine-like effects, ...

s are best based on lean body weight. The induction dose of propofol should also be based on LBW.''Stoelting's Anesthesia and Co-Existing Disease, 6th Edition. Pages 329-330.''

Estimation

LBM is usually estimated using mathematical formulas. Several formulas exist, having different utility for different purposes. For example, the Boer formula is method of choice for LBM estimation to calculate the dose given in contrast CT in obese individuals with BMI between 35 and 40. A

nomogram A nomogram (), also called a nomograph, alignment chart, or abac, is a graphical Analog computer, calculating device, a two-dimensional diagram designed to allow the approximate graphical computation of a Function (mathematics), mathematical fu ...

based on height, weight and arm circumference may be used.

Boer

The Boer formula is: For men: LBM = (0.407 × W) + (0.267 × H) − 19.2 For women: LBM = (0.252 × W) + (0.473 × H) − 48.3 where W is body weight in kilograms and H is body height in centimeters.

Hume

The following formula by Hume may be used: For men: LBM = (0.32810 × W) + (0.33929 × H) − 29.5336 For women: LBM = (0.29569 × W) + (0.41813 × H) − 43.2933 where W is body weight in kilograms and H is body height in centimeters.

Actual measurement

Instead of mathematical estimation the actual value of LBM may be calculated using various technologies such as

Dual-energy X-ray absorptiometry Dual-energy X-ray absorptiometry (DXA, or DEXA) is a means of measuring bone mineral density (BMD) with Spectral imaging (radiography), spectral imaging. Two X-ray beams, with different energy levels, are aimed at the patient's bones. When soft t ...

(DEXA).

References