Editing Body mass index (section)

==History==
[[File:Obesity & BMI.png|thumb|Obesity and BMI]]
[[Adolphe Quetelet]], a Belgian [[astronomer]], mathematician, [[statistician]], and [[sociologist]], devised the basis of the BMI between 1830 and 1850 as he developed what he called "social physics".<ref>{{cite journal |vauthors=Eknoyan G |date=January 2008 |title=Adolphe Quetelet (1796–1874) – the average man and indices of obesity |journal=Nephrology, Dialysis, Transplantation |volume=23 |issue=1 |pages=47–51 |doi=10.1093/ndt/gfm517 |pmid=17890752 |doi-access=}}</ref> Quetelet himself never intended for the index, then called the Quetelet Index, to be used as a means of medical assessment. Instead, it was a component of his study of {{lang|fr|l'homme moyen}}, or the average man. Quetelet thought of the average man as a social ideal, and developed the body mass index as a means of discovering the socially ideal human person.<ref name=":0" /> According to Lars Grue and Arvid Heiberg in the Scandinavian Journal of Disability Research, Quetelet's idealization of the average man would be elaborated upon by [[Francis Galton]] a decade later in the development of [[Eugenics]].<ref>{{Cite journal |last=Heiberg |first=Arvid |date=2006-11-04 |title=Notes on the History of Normality – Reflections on the Work of Quetelet and Galton |journal=Scandinavian Journal of Disability Research |language=en-US |volume=8 |issue=4 |pages=232–246 |doi=10.1080/15017410600608491|doi-access=free }}</ref>

The modern term "body mass index" (BMI) for the ratio of [[human body weight]] to squared height was coined in a paper published in the July 1972 edition of the ''[[Journal of Chronic Diseases]]'' by [[Ancel Keys]] and others. In this paper, Keys argued that what he termed the BMI was "if not fully satisfactory, at least as good as any other relative weight index as an indicator of relative obesity".<ref>{{cite journal | vauthors = Blackburn H, Jacobs D | title = Commentary: Origins and evolution of body mass index (BMI): continuing saga | journal = International Journal of Epidemiology | volume = 43 | issue = 3 | pages = 665–669 | date = June 2014 | pmid = 24691955 | doi = 10.1093/ije/dyu061 | url = https://academic.oup.com/ije/article-pdf/43/3/665/9728399/dyu061.pdf | doi-access = free }}</ref><ref>{{cite magazine |url= http://www.slate.com/id/2223095/ |title= Beyond BMI: Why doctors won't stop using an outdated measure for obesity | vauthors = Singer-Vine J |magazine= [[Slate (magazine)|Slate]] |date= July 20, 2009 |access-date= 15 December 2013 |url-status=live |archive-url= https://web.archive.org/web/20110907125413/http://www.slate.com/id/2223095 |archive-date= 7 September 2011 }}</ref><ref>{{cite journal | vauthors = Keys A, Fidanza F, Karvonen MJ, Kimura N, Taylor HL | title = Indices of relative weight and obesity | journal = Journal of Chronic Diseases | volume = 25 | issue = 6 | pages = 329–343 | date = July 1972 | pmid = 4650929 | doi = 10.1016/0021-9681(72)90027-6 }}</ref>

The interest in an index that measures [[body fat]] came with observed increasing obesity in prosperous [[Western world|Western]] societies. Keys explicitly judged BMI as appropriate for ''population'' studies and inappropriate for individual evaluation. Nevertheless, due to its simplicity, it has come to be widely used for preliminary diagnoses.<ref name=nhlbi>{{cite web|title= Assessing Your Weight and Health Risk|url= http://www.nhlbi.nih.gov/health/educational/lose_wt/risk.htm|publisher= National Heart, Lung and Blood Institute|access-date= 19 December 2014|url-status=live|archive-url= https://web.archive.org/web/20141219195703/http://www.nhlbi.nih.gov/health/educational/lose_wt/risk.htm|archive-date=19 December 2014}}</ref> Additional metrics, such as waist circumference, can be more useful.<ref name=nhsob>{{cite web|title= Defining obesity|url= http://www.nhs.uk/Conditions/Obesity/Pages/Introduction.aspx|publisher= [[National Health Service|NHS]]|access-date= 19 December 2014|url-status=live|archive-url= https://web.archive.org/web/20141218121754/http://www.nhs.uk/Conditions/Obesity/Pages/Introduction.aspx|archive-date= 18 December 2014}}</ref>
{{BMI calculator|float=right}}
The BMI is expressed in kg/m<sup>2</sup>, resulting from mass in kilograms and height in metres. If [[Pound (mass)|pounds]] and [[inch]]es are used, a conversion factor of 703&nbsp;(kg/m<sup>2</sup>)/(lb/in<sup>2</sup>) is applied. (If pounds and feet are used, a conversion factor of 4.88 is used.) When the term BMI is used informally, the units are usually omitted.

<math display="block">\mathrm{BMI} = \frac{\text{mass}_\text{kg}}{{\text{height}_\text{m}}^2}
= \frac{\text{mass}_\text{lb}}{{\text{height}_\text{in}}^2}\times 703</math>

BMI provides a simple numeric measure of a person's ''thickness'' or ''thinness'', allowing health professionals to discuss weight problems more objectively with their patients. BMI was designed to be used as a simple means of classifying average sedentary (physically inactive) populations, with an average [[body composition]].<ref name="WHO: Physical status">{{cite journal | vauthors = <!--Staff writer(s); no by-line.--> | title = Physical status: the use and interpretation of anthropometry. Report of a WHO Expert Committee | journal = World Health Organization Technical Report Series | volume = 854 | issue = 854 | pages = 1–452 | year = 1995 | pmid = 8594834 | url = <!-- derived from:http://www.who.int/childgrowth/publications/physical_status/en/-->http://whqlibdoc.who.int/trs/WHO_TRS_854.pdf | archive-url = https://web.archive.org/web/20070210134151/http://whqlibdoc.who.int/trs/WHO_TRS_854.pdf | url-status=live | archive-date = 2007-02-10 }}</ref> For such individuals, the BMI value recommendations {{as of | 2014 | lc = on}} are as follows: 18.5 to 24.9&nbsp;kg/m<sup>2</sup> may indicate optimal weight, lower than 18.5 may indicate [[underweight]], 25 to 29.9 may indicate [[overweight]], and 30 or more may indicate [[obesity|obese]].<ref name=nhlbi /><ref name=nhsob /> Lean male athletes often have a high muscle-to-fat ratio and therefore a BMI that is misleadingly high relative to their body-fat percentage.<ref name=nhsob />