"Center for Disease Body Mass Index: FAQ link
""""CDC:Body Mass Index (BMI) is a number calculated from a person's weight and height. BMI provides a reliable indicator of body fatness
for most people and is used to screen for weight categories that may lead to health problem"
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How reliable is BMI as an indicator of body fatness?
The correlation between the BMI number and body fatness is fairly strong; however the correlation varies by sex, race, and age. These variations include the following examples: 3, 4
At the same BMI, women tend to have more body fat than men.
At the same BMI, older people, on average, tend to have more body fat than younger adults.
Highly trained athletes may have a high BMI because of increased muscularity rather than increased body fatness.
It is also important to remember that BMI is only one factor related to risk for disease. For assessing someone's likelihood of developing overweight- or obesity-related diseases, the National Heart, Lung, and Blood Institute guidelines recommend looking at two other predictors:
The individual's waist circumference (because abdominal fat is a predictor of risk for obesity-related diseases).
Other risk factors the individual has for diseases and conditions associated with obesity (for example, high blood pressure or physical inactivity).
For more information about the assessment of health risk for developing overweight- and obesity-related diseases, visit the following Web pages from the National Heart, Lung, and Blood Institute:"""Assessing Your Risk
Body Mass Index Table
Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults