The risk for developing heart disease, the primary health-related killer in America, increases substantially if you are overweight or obese. The body mass index, or BMI, is an internationally used means of determining body fat percentage. It's meant to measure and possibly avoid preventable health disease. The BMI number is calculated similarly for male and female adults. The calculation for children is dependent on age and gender-specific factors, because body fat changes from childhood to adolescence and significantly differs between genders in youth.
BMI History
The first body mass index formulation was created in the 19th century and referred to as the Quetelet Index. According to Slate magazine, it was named for the Belgian mathematician Adolphe Quetelet, who coined the concept. Quetelet sought to quantify the measure of a normal man, and his initial efforts were not connected to health-related disease of the time. After testing his theory on hundreds of men, he found a correlation between height squared and weight. In 1972, a physiology and obesity researcher, Ancel Keys, further examined the Quetelet Index and renamed the calculation the body mass index. The BMI became useful as the proportions of obesity increased. During the 1980s, the National Institutes of Health recognized and defined this health condition by using the BMI calculation.
BMI Calculation
The simplest means to calculate your BMI is with an online tool available from credible resources at the Centers for Disease Control and Prevention or the National Heart, Lung and Blood Institute. The formula divides your weight by your height in standard or metric version. Determine your weight in pounds, then multiply this number by 703. Divide the result by your height in inches, then divide that result by your height in inches again. The final number is your BMI risk level number. The metric measurement requires that you divide your weight in kilograms by height in meters squared for the BMI result. The ranges for the BMI are based on the relationship between your weight and disease or death risk, the CDC says.
BMI Values and Interpretation
The BMI calculation yields the possible results of underweight, healthy, overweight and obese or extremely obese. According to the CDC, standard weight status categories for BMI are delineated numerically as 18.5 or below being underweight, 18.5 to 24.9 as normal healthy weight, 25.0 to 29.9 as overweight and 30.0 and above as obese or extremely obese. The higher your BMI, the more you are susceptible to risk for cardiovascular disease including stroke or coronary heart disease, Type 2 diabetes and certain cancers of the breast and colon. The BMI for teens and children is based on a percentile range. Get them screened by a pediatrician to ensure an accurate result.
Limitations of the BMI
The BMI is a fairly strong indicator of fat, but the calculation doesn't take into account that females have a higher fat percentage than males or that elderly people tend to have more fat than young adults. Athletes and bodybuilders also tend to have skewed BMI because they have a higher percentage of muscularity over fat that causes weight increase. Ethnicity is also a factor in fat proportions, frame size and risk level. Although the BMI is used by medical professionals as a tool for treatment planning, use of the calculation is available to anyone without training on how to utilize the results. The National Heart, Lung and Blood Institute advises to also consider your waist circumference and other risk factors associated with obesity such as blood pressure, activity level and cholesterol.
References
- Centers for Disease Control and Prevention: About BMI for Adults
- National Heart, Lung and Blood Institute: Assessing Your Weight and Health Risk
- American Heart Association: Frequently Asked Questions About BMI
- Slate magazine: Beyond BMI; Jeremy Singer-Vine; July 2009
- European Union Public Health Information System: Overweight
- MedlinePlus: Body Mass Index
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