Editing Body mass index (section)

{{Short description|Relative weight based on mass and height}}
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{{Infobox diagnostic
| name = Body mass index (BMI)
| synonyms = Quetelet index
| image = BMI chart.png
| alt =
| caption = Chart showing body mass index (BMI) for a range of heights and weights in both metric and imperial. Colours indicate [[#Categories|BMI categories]] defined by the [[World Health Organization]]; ''underweight'', ''normal weight'', ''overweight'', ''moderately obese'', ''severely obese'' and ''very severely obese''.
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| MedlinePlus = 007196
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{{Human body weight}}

'''Body mass index''' ('''BMI''') is a value derived from the [[mass]] ([[Mass versus weight|weight]]) and [[height]] of a person. The BMI is defined as the [[human body weight|body mass]] divided by the [[square (algebra)|square]] of the [[human height|body height]], and is expressed in [[Units of measurement|units]] of kg/m<sup>2</sup>, resulting from mass in [[kilogram]]s (kg) and height in [[metre]]s (m).

The BMI may be determined first by measuring its components by means of a [[weighing scale]] and a [[stadiometer]]. The multiplication and division may be carried out directly, by hand or using a calculator, or indirectly using a [[lookup table]] (or chart).{{efn|e.g., the {{cite web | url = http://www.nhlbi.nih.gov/guidelines/obesity/bmi_tbl.htm | title = Body Mass Index Table | archive-url = https://web.archive.org/web/20100310114919/http://www.nhlbi.nih.gov/guidelines/obesity/bmi_tbl.htm | archive-date=2010-03-10 | publisher = [[National Institutes of Health]]'s [[National Heart, Lung, and Blood Institute|NHLBI]] }}}} The table displays BMI as a function of mass and height and may show other units of measurement (converted to [[Metric system|metric units]] for the calculation).{{efn|For example, in the UK where people often know their weight in [[Stone (unit)|stone]] and height in feet and inches – see {{cite news |url=http://news.bbc.co.uk/2/hi/health/5297790.stm |title=Calculate your body mass index |date=30 August 2006 |access-date=2019-12-11 }}}} The table may also show contour lines or colours for different BMI categories.

The BMI is a convenient [[rule of thumb]] used to broadly categorize a person as based on tissue mass ([[muscle]], [[fat]], and [[bone]]) and height. Major adult BMI classifications are ''[[underweight]]'' (under 18.5 kg/m<sup>2</sup>), ''[[Human body weight#Ideal_body_weight|normal weight]]'' (18.5 to 24.9), ''[[overweight]]'' (25 to 29.9), and ''[[obese]]'' (30 or more).<ref name="World Health Organization 2006" /> When used to predict an individual's health, rather than as a statistical measurement for groups, the BMI has [[#Limitations|limitations]] that can make it less useful than some of the [[#Alternatives|alternatives]], especially when applied to individuals with [[abdominal obesity]], [[short stature]], or [[Bodybuilding|high muscle mass]].

BMIs under 20 and over 25 have been associated with higher all-cause mortality, with the risk increasing with distance from the 20–25 range.<ref>{{cite journal | vauthors = Di Angelantonio E, Bhupathiraju S, Wormser D, Gao P, Kaptoge S, Berrington de Gonzalez A, Cairns BJ, Huxley R, Jackson C, Joshy G, Lewington S, Manson JE, Murphy N, Patel AV, Samet JM, Woodward M, Zheng W, Zhou M, Bansal N, Barricarte A, Carter B, Cerhan JR, Smith GD, Fang X, Franco OH, Green J, Halsey J, Hildebrand JS, Jung KJ, Korda RJ, McLerran DF, Moore SC, O'Keeffe LM, Paige E, Ramond A, Reeves GK, Rolland B, Sacerdote C, Sattar N, Sofianopoulou E, Stevens J, Thun M, Ueshima H, Yang L, Yun YD, Willeit P, Banks E, Beral V, Chen Z, Gapstur SM, Gunter MJ, Hartge P, Jee SH, Lam TH, Peto R, Potter JD, Willett WC, Thompson SG, Danesh J, Hu FB | title = Body-mass index and all-cause mortality: individual-participant-data meta-analysis of 239 prospective studies in four continents | journal = Lancet | volume = 388 | issue = 10046 | pages = 776–86 | date = August 2016 | pmid = 27423262 | pmc = 4995441 | doi = 10.1016/S0140-6736(16)30175-1 }}</ref>
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