Lean body mass (LBM), sometimes conflated with ''fat-free mass'', is a component of

body composition In physical fitness, body composition is used to describe the percentages of fat, bone, water, and muscle in human bodies. Because muscular tissue takes up less space in the body than fat tissue, body composition, as well as weight, determines ...

. Fat free mass (FFM) is calculated by subtracting

body fat Adipose tissue, body fat, or simply fat is a loose connective tissue composed mostly of adipocytes. In addition to adipocytes, adipose tissue contains the stromal vascular fraction (SVF) of cells including preadipocytes, fibroblasts, vascular e ...

weight from total

body weight Human body weight is a person's mass or weight. Strictly speaking, body weight is the measurement of weight without items located on the person. Practically though, body weight may be measured with clothes on, but without shoes or heavy accessor ...

: 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 membrane The cell membrane (also known as the plasma membrane (PM) or cytoplasmic membrane, and historically referred to as the plasmalemma) is a biological membrane that separates and protects the interior of all cells from the outside environment (th ...

s 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) The percentage of total body mass that is lean is usually not quoted – it would typically be 60–90%. Instead, the

body fat percentage The body fat percentage (BFP) of a human or other living being is the total mass of fat divided by total body mass, multiplied by 100; body fat includes essential body fat and storage body fat. Essential body fat is necessary to maintain life and ...

, 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 el, μεταβολή ''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 ...

. 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 substances that act on opioid receptors to produce morphine-like effects. Medically they are primarily used for pain relief, including anesthesia. Other medical uses include suppression of diarrhea, replacement therapy for opioid use ...

s are best based on lean body weight. The induction dose of

propofol Propofol, marketed as Diprivan, among other names, is a short-acting medication that results in a decreased level of consciousness and a lack of memory for events. Its uses include the starting and maintenance of general anesthesia, sedation f ...

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 Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...

individuals with BMI between 35 and 40. A nomogram 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 (DEXA).

References

{{DEFAULTSORT:Lean body mass Body shape Human body weight Ratios