BMI stands for body mass index. It is a common measure that is easily calculated if you know your height and weight, in either metric or U.S. customary system. It estimates body fat. BMI is calculated by dividing your weight by your height squared. BMI is used by many clinicians and researchers to assess a patient's or subject's weight status and associated potential disease risk factors.
BMI Classifications
You are classified as underweight, normal weight, overweight or obese based on BMI calculations. Your BMI falls into one of four ranges: underweight -- less than 18.5; normal weight -- 18.5 to 24.9; overweight -- 25-29.9 or obese -- 30 or greater.
Further classification is sometimes used to define a BMI of 40 or greater as morbidly obese. For adults ages 18 to 65, a normal BMI of 18.5 to 24.9 is considered a healthy BMI.
Limitations to BMI
For most male and female adults, BMI is a accurate assessment of body fat. However, for few specific populations, BMI results may be skewed. If you have a great deal of muscle mass, your BMI may measure high, even with very little body fat. This is because muscle weighs more than fat, thus body fat is overestimated. In the opposite case, individuals, such as the elderly, with very low muscle mass may have underestimated BMIs.
BMI and Associated Risks
It is important to know your BMI as BMI classifications have been correlated to your risk of disease. With a BMI of greater than 25, you have an increased likelihood of developing heart disease, high blood pressure, sleep apnea, type II diabetes and varicose veins. For the elderly population, a lower BMI is associated with an increased risk of osteoporosis and fractures related to falls.
Know Your BMI
You can easily calculate your BMI.Divide your weight in pounds by your height squared and in inches. Then multiply the number you get by 703 and that is your BMI. Another option is to use the many websites available online that calculate your BMI for you. A standard and reliable BMI calculate can be found at nhlbisupport.com/bmi/.
References
- National Heart Lung and Blood Institute: Assessing your weight and health risk
- MedLine Plus: Body Mass Index
- "Proceedings of the Nutrition Society"; Use of BMI in the Assessment of Undernutrition in Older Subjects: Reflecting on Practice; Cook et al; 2005.
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