Editing Body mass index (section)

==Categories==
A common use of the BMI is to assess how far an individual's body weight departs from what is normal for a person's height. The weight excess or deficiency may, in part, be accounted for by body fat ([[adipose tissue]]) although other factors such as muscularity also affect BMI significantly (see discussion below and [[overweight]]).<ref>{{Cite web|url=https://www.cdc.gov/healthyweight/assessing/bmi/adult_bmi/index.html|title=About Adult BMI {{!}} Healthy Weight|date=2017-08-29|website=CDC|language=en-us|access-date=2018-01-26}}</ref>

The [[World Health Organization|WHO]] regards an adult BMI of less than 18.5 as underweight and possibly indicative of [[malnutrition]], an [[eating disorder]], or other health problems, while a BMI of 25 or more is considered overweight and 30 or more is considered [[obesity|obese]].<ref name="World Health Organization 2006">{{cite book |url=https://apps.who.int/iris/bitstream/handle/10665/43190/9241593024_eng.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://apps.who.int/iris/bitstream/handle/10665/43190/9241593024_eng.pdf |archive-date=2022-10-09 |url-status=live |title=The SuRF Report 2 |series=The Surveillance of Risk Factors Report Series (SuRF) |page=22 |publisher=World Health Organization |date=2005 |ref={{harvid|World Health Organization|2005}}}}</ref> In addition to the principle, international WHO BMI cut-off points (16, 17, 18.5, 25, 30, 35 and 40), four additional cut-off points for at-risk Asians were identified (23, 27.5, 32.5 and 37.5).{{sfn|World Health Organization|2005|pp=21–22}} These ranges of BMI values are valid only as statistical categories.

{| class="wikitable plainrowheaders" style="text-align:center"
|+ BMI, basic categories
|-
! scope="col"| Category
! scope="col"| BMI (kg/m<sup>2</sup>){{efn|name="range-precision"}}
! scope="col"| [[#BMI prime (exponent of 2, normalization factor)|BMI Prime]]{{efn|name="range-precision"}}
|-
! scope="row"| Underweight (Severe thinness)
| < 16.0
| < 0.64
|-
! scope="row"| Underweight (Moderate thinness)
| class="nowrap"| 16.0–17.0
| class="nowrap"| 0.64–0.68
|-
! scope="row"| Underweight (Mild thinness)
| 17.0–18.5
| 0.68–0.74
|-
! scope="row"| Normal range
| 18.5–25.0
| 0.74–1.00
|-
! scope="row"| Overweight (Pre-obese)
| 25.0–30.0
| 1.00–1.20
|-
! scope="row"| Obese (Class I)
| 30.0–35.0
| 1.20–1.40
|-
! scope="row"| Obese (Class II)
| 35.0–40.0
| 1.40–1.60
|-
! scope="row"| Obese (Class III)
| ≥ 40.0
| ≥ 1.60
|}

===Children and youth===
[[File:BMIBoys 1.svg|thumb|upright=1.7|BMI for age percentiles for boys 2 to 20 years of age]]
[[File:BMIGirls 1.svg|thumb|upright=1.7|BMI for age percentiles for girls 2 to 20 years of age]]
BMI is used differently for people aged 2 to 20. It is calculated in the same way as for adults but then compared to typical values for other children or youth of the same age. Instead of comparison against fixed thresholds for underweight and overweight, the BMI is compared against the [[percentile]]s for children of the same sex and age.<ref>{{cite web|url = https://www.cdc.gov/nccdphp/dnpa/healthyweight/assessing/bmi/childrens_BMI/about_childrens_BMI.htm|title = Body Mass Index: BMI for Children and Teens|publisher = Center for Disease Control|access-date = 2013-12-16|url-status=live|archive-url = https://web.archive.org/web/20131029061522/http://www.cdc.gov/nccdphp/dnpa/healthyweight/assessing/bmi/childrens_BMI/about_childrens_BMI.htm|archive-date = 2013-10-29}}</ref>

A BMI that is less than the 5th percentile is considered underweight and above the 95th percentile is considered obese. Children with a BMI between the 85th and 95th percentile are considered to be overweight.<ref>{{cite book | chapter = Chapter 2: Use of Percentiles and Z-Scores in Anthropometry | title = Handbook of Anthropometry| vauthors = Wang Y |publisher=Springer|year=2012|isbn=978-1-4419-1787-4|location=New York|pages=29}}</ref>

Studies in Britain from 2013 have indicated that females between the ages 12 and 16 had a higher BMI than males of the same age by 1.0&nbsp;kg/m<sup>2</sup> on average.<ref>{{cite web|url = http://www.archive2.official-documents.co.uk/document/deps/doh/survey02/summ03.htm|title = Health Survey for England: The Health of Children and Young People|website = Archive2.official-documents.co.uk|access-date = 16 December 2013|url-status=dead|archive-url = https://web.archive.org/web/20120625003857/http://www.archive2.official-documents.co.uk/document/deps/doh/survey02/summ03.htm|archive-date = 2012-06-25}}</ref>

===International variations===
These recommended distinctions along the linear scale may vary from time to time and country to country, making global, longitudinal surveys problematic. People from different populations and descent have different associations between BMI, percentage of body fat, and health risks, with a higher risk of [[type 2 diabetes mellitus]] and [[Atherosclerosis|atherosclerotic]] cardiovascular disease at BMIs lower than the [[World Health Organization|WHO]] cut-off point for overweight, 25&nbsp;kg/m<sup>2</sup>, although the cut-off for observed risk varies among different populations. The cut-off for observed risk varies based on populations and subpopulations in Europe, Asia and Africa.<ref>{{cite journal| vauthors = Ogunlade O, Adalumo OA, Asafa MA |title= Challenges of body mass index classification: New criteria for young adult Nigerians|journal= Niger J Health Sci |year=2015|volume= 15|issue=15:71–4|page= 71|doi= 10.4103/1596-4078.182319|doi-broken-date= 1 November 2024|s2cid= 132117809|doi-access= free}}</ref><ref>{{cite journal | title = Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies | journal = Lancet | volume = 363 | issue = 9403 | pages = 157–163 | date = January 2004 | pmid = 14726171 | doi = 10.1016/S0140-6736(03)15268-3 | author1 = WHO Expert Consultation | s2cid = 15637224 }}</ref>

====Hong Kong====
The [[Hospital Authority]] of [[Hong Kong]] recommends the use of the following BMI ranges:<ref name="ha">{{cite web |url=https://www.fitnessofbody.com/2019/04/body-weight-chart.html |title=Body weight chart – ideal goal weight chart |publisher=Fitness of Body – Health & Wellness site |language=en |access-date=2019-04-21 |archive-date=2021-03-08 |archive-url=https://web.archive.org/web/20210308091202/https://www.fitnessofbody.com/2019/04/body-weight-chart.html |url-status=dead }}</ref>

{| class="wikitable plainrowheaders" style="text-align:center"
|+ BMI in Hong Kong
|-
! scope="col"| Category
! scope="col"| BMI (kg/m<sup>2</sup>){{efn|name="range-precision"}}
|-
! scope="row"| Underweight (Unhealthy)
| < 18.5
|-
! scope="row"| Normal range (Healthy)
| class="nowrap"| 18.5–22.9
|-
! scope="row"| Overweight I (At risk)
| 23.0–24.9
|-
! scope="row"| Overweight II (Moderately obese)
| 25.0–29.9
|-
! scope="row"| Overweight III (Severely obese)
| ≥ 30.0
|}

====Japan====
A 2000 study from the Japan Society for the Study of Obesity (JASSO) presents the following table of BMI categories:<ref name="himan-mhlw">{{cite web |url=http://www.mhlw.go.jp/topics/bukyoku/kenkou/seikatu/himan/about.html |title={{as written|肥満って、 どんな状態？}} |trans-title=What is obesity, what kind of state? |work=Obesity Homepage<!--肥満ホームページ--> |publisher=Ministry of Health, Labor and Welfare<!--厚生労働省--> |access-date=2013-05-25 |language=ja |url-status=dead |archive-url=https://web.archive.org/web/20130628232937/http://www.mhlw.go.jp/topics/bukyoku/kenkou/seikatu/himan/about.html |archive-date=2013-06-28 }}</ref><ref>{{cite journal | vauthors = Shiwaku K, Anuurad E, Enkhmaa B, Nogi A, Kitajima K, Shimono K, Yamane Y, Oyunsuren T | title = Overweight Japanese with body mass indexes of 23.0–24.9 have higher risks for obesity-associated disorders: a comparison of Japanese and Mongolians | journal = International Journal of Obesity and Related Metabolic Disorders | volume = 28 | issue = 1 | pages = 152–158 | date = January 2004 | pmid = 14557832 | doi = 10.1038/sj.ijo.0802486 | s2cid = 287574 | doi-access =  }}</ref><ref>{{cite journal | vauthors = Kanazawa M, Yoshiike N, Osaka T, Numba Y, Zimmet P, Inoue S | title = Criteria and classification of obesity in Japan and Asia-Oceania. | journal = Asia Pacific Journal of Clinical Nutrition | date = December 2002 | volume = 11 | pages = S732-7 | doi = 10.1046/j.1440-6047.11.s8.19.x | url = https://apjcn.nhri.org.tw/server/APJCN/11/s7/S732.pdf }}{{rp| S734}}</ref>

{| class="wikitable plainrowheaders" style="text-align:center"
|+ BMI in Japan
|-
! scope="col"| Category
! scope="col"| BMI (kg/m<sup>2</sup>){{efn|name="range-precision"}}
|-
! scope="row"| Underweight (Thin)
| < 18.5
|-
! scope="row"| Normal weight
| class="nowrap"| 18.5–24.9
|-
! scope="row"| Obesity (Class 1)
| 25.0–29.9
|-
! scope="row"| Obesity (Class 2)
| 30.0–34.9
|-
! scope="row"| Obesity (Class 3)
| 35.0–39.9
|-
! scope="row"| Obesity (Class 4)
| ≥ 40.0
|}

====Singapore====
In Singapore, the BMI cut-off figures were revised in 2005 by the [[Health Promotion Board]] (HPB), motivated by studies showing that many Asian populations, including Singaporeans, have a higher proportion of body fat and increased risk for cardiovascular diseases and [[diabetes mellitus]], compared with general BMI recommendations in other countries. The BMI cut-offs are presented with an emphasis on health risk rather than weight.<ref>{{cite web |url=http://cardiology.com.sg/body-mass-index-bmi/|title=Body Mass Index (BMI) |website=Peter Yan Cardiology Clinic |access-date=8 July 2021}}</ref>

{| class="wikitable plainrowheaders"
|+ BMI in Singapore
|-
! scope="col"| Category
! scope="col"| BMI (kg/m<sup>2</sup>){{efn|name="range-precision"}}
! scope="col"| Health risk
|-
! scope="row"| Underweight
| style="text-align:center"| < 18.5
| Possible nutritional deficiency and osteoporosis.
|-
! scope="row"| Normal
| style="text-align:center" class="nowrap"| 18.5–22.9
| Low risk (healthy range).
|-
! scope="row"| Mild to moderate overweight
| style="text-align:center"| 23.0–27.4
| Moderate risk of developing heart disease, high blood pressure, stroke, diabetes mellitus.
|-
! scope="row"| Very overweight to obese
| style="text-align:center"| ≥ 27.5
| High risk of developing heart disease, high blood pressure, stroke, diabetes mellitus. [[Metabolic syndrome]].
|}

==== United Kingdom ====
In the UK, [[National Institute for Health and Care Excellence|NICE]] guidance recommends prevention of type 2 diabetes should start at a BMI of 30 in White and 27.5 in [[Black British people|Black African]], [[British African-Caribbean people|African-Caribbean]], [[South Asians in the United Kingdom|South Asian]], and [[British Chinese|Chinese]] populations.<ref>{{Cite journal |date=2022-07-26 |title=Diabetes: putting people at the heart of services |url=https://evidence.nihr.ac.uk/collection/diabetes-putting-people-at-the-heart-of-services/ |journal=NIHR Evidence |type=Plain English summary |language=en |publisher=National Institute for Health and Care Research |doi=10.3310/nihrevidence_52026 |s2cid=251299176|url-access=subscription }}</ref>

Research since 2021 based on a large sample of almost 1.5 million people in England found that some ethnic groups would benefit from prevention at or above a BMI of (rounded):<ref>{{Cite journal |date=2022-03-10 |title=Are you at risk of diabetes? Research finds prevention should start at a different BMI for each ethnic group |url=https://evidence.nihr.ac.uk/alert/diabetes-prevention-should-start-at-different-bmi-for-each-ethnic-group/ |journal=NIHR Evidence |type=Plain English summary |language=en |publisher=National Institute for Health and Care Research |doi=10.3310/alert_48878 |s2cid=247390548|url-access=subscription }}</ref><ref>{{cite journal | vauthors = Caleyachetty R, Barber TM, Mohammed NI, Cappuccio FP, Hardy R, Mathur R, Banerjee A, Gill P | title = Ethnicity-specific BMI cutoffs for obesity based on type 2 diabetes risk in England: a population-based cohort study | journal = The Lancet. Diabetes & Endocrinology | volume = 9 | issue = 7 | pages = 419–426 | date = July 2021 | pmid = 33989535 | pmc = 8208895 | doi = 10.1016/S2213-8587(21)00088-7 }}</ref>
* 30 in White
* 28 in Black
** just below 30 in Black British
** 29 in Black African
** 27 in Black Other
** 26 in Black Caribbean
* 27 in Arab and Chinese
* 24 in South Asian
** 24 in Pakistani, Indian and Nepali
** 23 in Tamil and Sri Lankan
** 21 in [[British Bangladeshis|Bangladeshi]]

====United States====
In 1998, the U.S. [[National Institutes of Health]] brought U.S. definitions in line with [[World Health Organization]] guidelines, lowering the normal/overweight cut-off from a BMI of 27.8 (men) and 27.3 (women) to a BMI of 25. This had the effect of redefining approximately 25 million Americans, previously ''healthy'', to ''overweight''.<ref name = "CNN_1998">{{cite news | url=http://www.cnn.com/HEALTH/9806/17/weight.guidelines/ | title=Who's fat? New definition adopted | publisher=CNN | date=June 17, 1998 | access-date=2010-04-26 | url-status=live | archive-url=https://web.archive.org/web/20101122173108/http://www.cnn.com/HEALTH/9806/17/weight.guidelines/ | archive-date=November 22, 2010 }}</ref><ref>{{cite journal |last=Nuttall |first=Frank Q. |date=2015-04-07 |title=Body Mass Index – Obesity, BMI, and Health: A Critical Review |journal=Nutrition Today |volume=50 |issue=3 |pages=117–128 |doi=10.1097/NT.0000000000000092 |pmc=4890841 |pmid=27340299}}</ref>

This can partially explain the increase in the ''overweight'' diagnosis in the past 20 years,{{when|date=February 2023}} and the increase in sales of weight loss products during the same time. [[World Health Organization|WHO]] also recommends lowering the normal/overweight threshold for southeast Asian body types to around BMI 23, and expects further revisions to emerge from clinical studies of different body types.<ref>{{Cite journal|last=World Health Organization|date=January 10, 2004|title=Appropriate body-mass index for Asian populations and its implications for policy and intervention strategies|url=https://www.who.int/nutrition/publications/bmi_asia_strategies.pdf|archive-url=https://web.archive.org/web/20061210180811/http://www.who.int/nutrition/publications/bmi_asia_strategies.pdf|url-status=dead|archive-date=December 10, 2006|journal=The Lancet|volume=363|issue=9403|pages=157–163|doi=10.1016/s0140-6736(03)15268-3|pmid=14726171|s2cid=15637224}}</ref>

A survey in 2007 showed 63% of Americans were then overweight or obese, with 26% in the obese category (a BMI of 30 or more). By 2014, 37.7% of adults in the United States were obese, 35.0% of men and 40.4% of women; class 3 obesity (BMI over 40) values were 7.7% for men and 9.9% for women.<ref>{{cite journal | vauthors = Flegal KM, Kruszon-Moran D, Carroll MD, Fryar CD, Ogden CL | title = Trends in Obesity Among Adults in the United States, 2005 to 2014 | journal = JAMA | volume = 315 | issue = 21 | pages = 2284–2291 | date = June 2016 | pmid = 27272580 | doi = 10.1001/jama.2016.6458 | doi-access = free | pmc = 11197437 }}</ref> The U.S. National Health and Nutrition Examination Survey of 2015–2016 showed that 71.6% of American men and women had BMIs over 25.<ref>{{cite web|url=https://www.cdc.gov/nchs/data/hus/2018/021.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://www.cdc.gov/nchs/data/hus/2018/021.pdf |archive-date=2022-10-09 |url-status=live|title= Selected health conditions and risk factors, by age: the United States, selected years}}</ref> Obesity—a BMI of 30 or more—was found in 39.8% of the US adults.

<div>
{| class="wikitable plainrowheaders floatleft"
|-
|+ Body mass index values (kg/m<sup>2</sup>) for males aged 20 and over, and selected percentiles by age: United States, 2011–2014<ref name="CDC-Anthropometric">{{cite web|url=https://www.cdc.gov/nchs/data/series/sr_03/sr03_039.pdf|title=Anthropometric Reference Data for Children and Adults: United States|publisher=[[Centers for Disease Control and Prevention|CDC DHHS]]|date=2016|url-status=live|archive-url=https://web.archive.org/web/20170202010330/https://www.cdc.gov/nchs/data/series/sr_03/sr03_039.pdf|archive-date=2017-02-02}}</ref>
|-
! scope="col" rowspan="2"| Age
! scope="colgroup" colspan="9"| Percentile
|-
! scope="col"| 5th
! scope="col"| 10th
! scope="col"| 15th
! scope="col"| 25th
! scope="col"| 50th
! scope="col"| 75th
! scope="col"| 85th
! scope="col"| 90th
! scope="col"| 95th
|-
! scope="row" style="text-align:center"| ≥ 20 (total)
| 20.7
| 22.2
| 23.0
| 24.6
| 27.7
| 31.6
| 34.0
| 36.1
| 39.8
|-
! scope="row" style="text-align:center" class="nowrap"| 20–29
| 19.3
| 20.5
| 21.2
| 22.5
| 25.5
| 30.5
| 33.1
| 35.1
| 39.2
|-
! scope="row" style="text-align:center"| 30–39
| 21.1
| 22.4
| 23.3
| 24.8
| 27.5
| 31.9
| 35.1
| 36.5
| 39.3
|-
! scope="row" style="text-align:center"| 40–49
| 21.9
| 23.4
| 24.3
| 25.7
| 28.5
| 31.9
| 34.4
| 36.5
| 40.0
|-
! scope="row" style="text-align:center"| 50–59
| 21.6
| 22.7
| 23.6
| 25.4
| 28.3
| 32.0
| 34.0
| 35.2
| 40.3
|-
! scope="row" style="text-align:center"| 60–69
| 21.6
| 22.7
| 23.6
| 25.3
| 28.0
| 32.4
| 35.3
| 36.9
| 41.2
|-
! scope="row" style="text-align:center"| 70–79
| 21.5
| 23.2
| 23.9
| 25.4
| 27.8
| 30.9
| 33.1
| 34.9
| 38.9
|-
! scope="row" style="text-align:center"| ≥ 80
| 20.0
| 21.5
| 22.5
| 24.1
| 26.3
| 29.0
| 31.1
| 32.3
| 33.8
|}

{| class="wikitable plainrowheaders"
|-
|+ Body mass index values (kg/m<sup>2</sup>) for females aged 20 and over, and selected percentiles by age: United States, 2011–2014<ref name="CDC-Anthropometric" />
|-
! scope="col" rowspan="2"| Age
! scope="colgroup" colspan="9"| Percentile
|-
! scope="col"| 5th
! scope="col"| 10th
! scope="col"| 15th
! scope="col"| 25th
! scope="col"| 50th
! scope="col"| 75th
! scope="col"| 85th
! scope="col"| 90th
! scope="col"| 95th
|-
! scope="row" style="text-align:center"| ≥ 20 (total)
| 19.6
| 21.0
| 22.0
| 23.6
| 27.7
| 33.2
| 36.5
| 39.3
| 43.3
|-
! scope="row" style="text-align:center" class="nowrap"| 20–29
| 18.6
| 19.8
| 20.7
| 21.9
| 25.6
| 31.8
| 36.0
| 38.9
| 42.0
|-
! scope="row" style="text-align:center"| 30–39
| 19.8
| 21.1
| 22.0
| 23.3
| 27.6
| 33.1
| 36.6
| 40.0
| 44.7
|-
! scope="row" style="text-align:center"| 40–49
| 20.0
| 21.5
| 22.5
| 23.7
| 28.1
| 33.4
| 37.0
| 39.6
| 44.5
|-
! scope="row" style="text-align:center"| 50–59
| 19.9
| 21.5
| 22.2
| 24.5
| 28.6
| 34.4
| 38.3
| 40.7
| 45.2
|-
! scope="row" style="text-align:center"| 60–69
| 20.0
| 21.7
| 23.0
| 24.5
| 28.9
| 33.4
| 36.1
| 38.7
| 41.8
|-
! scope="row" style="text-align:center"| 70–79
| 20.5
| 22.1
| 22.9
| 24.6
| 28.3
| 33.4
| 36.5
| 39.1
| 42.9
|-
! scope="row" style="text-align:center"| ≥ 80
| 19.3
| 20.4
| 21.3
| 23.3
| 26.1
| 29.7
| 30.9
| 32.8
| 35.2
|}
{{clear}}
</div>