what is BMI?
Your Body Mass Index – or BMI – is a measure of your weight in relation to your height. Established by the National Institutes of Health in 1998, BMI provides a fairly accurate estimate of body fatness for most people. It’s an easy way to look at weight issues that may lead to health problems.

how is it used?
BMI is used as a screening tool to identify possible weight problems for adults. However, BMI is not a diagnostic tool. For example, a person may have a high BMI without being at a high risk for health problems. However, to determine if excess weight is a health risk, a healthcare provider would need to perform further assessments. These assessments might include skin-fold thickness measurements, evaluations of diet, physical activity, family history, and other appropriate health screenings.

are BMIs applicable to everyone?
BMI scores apply to adults, both men and women. But BMI scores for children and teens are a different matter. You should discuss those with a pediatrician.

how accurate is it?
According to the U.S. Centers for Disease Control (CDC), the correlation between the BMI number and body fatness is fairly strong. But that correlation varies by sex, race, and age.^{1, 2} For example:

• 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 weight is only one factor related to health risk. Other factors include diet, physical activity, family history, blood pressure, abdominal fat and cholesterol. If you have questions or concerns about the appropriateness of your weight, you should discuss them with your healthcare provider.

*Prentice AM and Jebb SA. Beyond Body Mass Index. Obesity Reviews. 2001 August; 2(3): 141–7. 2Gallagher D, et al. How useful is BMI for comparison of body fatness across age, sex and ethnic groups? American Journal of Epidemiology 1996;143:228–239.