Body mass index: Difference between revisions
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<math> \textrm{BMI} = \frac{ \textrm{W (kg)}}{\textrm{H (m)}^{2}} = 4.88 \frac{ \textrm{W (lbs)}}{\textrm{H (ft.)}^{2}} = 703 \frac{ \textrm{W (lbs.)}}{\textrm{H (in.)}^{2}}</math>. | <math> \textrm{BMI} = \frac{ \textrm{W (kg)}}{\textrm{H (m)}^{2}} = 4.88 \frac{ \textrm{W (lbs)}}{\textrm{H (ft.)}^{2}} = 703 \frac{ \textrm{W (lbs.)}}{\textrm{H (in.)}^{2}}</math>. | ||
Healthy BMI is between 18.5 and 24.9. Less than 18.5 is considered underweight; between 25 and 29.9 is considered overweight, over 30 is considered [[obesity|obese]], and over | Healthy BMI is between 18.5 and 24.9. Less than 18.5 is considered underweight; between 25 and 29.9 is considered overweight, over 30 is considered [[obesity|obese]], and over 45 is considered morbidly obese. | ||
BMI is a rough diagnostic tool for estimating body fat, and has limitations. Chief among these are that it may overestimate body fat in athletes and others who have a muscular build, and that it may underestimate body fat in older persons and others who have lost muscle mass.<ref>http://www.nhlbi.nih.gov/health/public/heart/obesity/lose_wt/risk.htm#limitations</ref> | BMI is a rough diagnostic tool for estimating body fat, and has limitations. Chief among these are that it may overestimate body fat in athletes and others who have a muscular build, and that it may underestimate body fat in older persons and others who have lost muscle mass.<ref>http://www.nhlbi.nih.gov/health/public/heart/obesity/lose_wt/risk.htm#limitations</ref> | ||
Another limitation is in the choice of exponent. If humans scaled proportionally in all three dimensions as they become taller, the appropriate exponent would be 3, instead of the 2 used for BMI calculation. However, 2 is too low. Data from the United States indicates that an exponent of 2.6 is most appropriate.<ref>{{cite web|url=http://www.math.utah.edu/~korevaar/ACCESS2003/bmi.pdf|title=Notes on Body Mass Index and actual national data|date=July 2003|author=Nick Korevaar|publisher=University of Utah Math Department|format=PDF}}</ref> Relatedly, the government of [[Singapore]] has set different cutoff levels of BMI, based on the shorter average stature and somewhat different body shape of Southeast Asians as compared to Europeans.<ref>{{cite web|url=http://www.hpb.gov.sg/hpb/default.asp?TEMPORARY_DOCUMENT=1769&TEMPORARY_TEMPLATE=2|title=Revision of Body Mass Index (BMI) Cut-offs in Singapore|date=2005-03-16|publisher=Health Promotion Board}}</ref> | |||
==Notes== | ==Notes== | ||
{{reflist}} | {{reflist}} | ||
Revision as of 23:08, 14 October 2008
Body mass index (abbreviated BMI) is a rough measure of proportionality between a person's height and weight, and is used to estimate whether a person is at a healthy weight for their height. BMI is calculated as weight in kilograms divided by height in meters squared. For english units, a conversion factor is applied.
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Healthy BMI is between 18.5 and 24.9. Less than 18.5 is considered underweight; between 25 and 29.9 is considered overweight, over 30 is considered obese, and over 45 is considered morbidly obese.
BMI is a rough diagnostic tool for estimating body fat, and has limitations. Chief among these are that it may overestimate body fat in athletes and others who have a muscular build, and that it may underestimate body fat in older persons and others who have lost muscle mass.[1]
Another limitation is in the choice of exponent. If humans scaled proportionally in all three dimensions as they become taller, the appropriate exponent would be 3, instead of the 2 used for BMI calculation. However, 2 is too low. Data from the United States indicates that an exponent of 2.6 is most appropriate.[2] Relatedly, the government of Singapore has set different cutoff levels of BMI, based on the shorter average stature and somewhat different body shape of Southeast Asians as compared to Europeans.[3]
Notes
- ↑ http://www.nhlbi.nih.gov/health/public/heart/obesity/lose_wt/risk.htm#limitations
- ↑ Nick Korevaar (July 2003). Notes on Body Mass Index and actual national data (PDF). University of Utah Math Department.
- ↑ Revision of Body Mass Index (BMI) Cut-offs in Singapore. Health Promotion Board (2005-03-16).