Body Mass Index (BMI)
Body Mass Index is a weight for stature index that can be utilized in conjunction with other health profile traits to indicate possible risk for disease. Because the percentage of body fat changes during the growing years, children and teens require adaptation of the BMI results to reflect this. The Body Mass Index Percentile identifies the place on the growth charts where a particular student compares with other students of the same gender and age.
The Centers for Disease Control and Prevention have suggested that Body Mass Index percentiles less than 5% and more than 85% may represent risk to health.
Neither the BMI nor the BMI% is a diagnostic tool. The student’s health care provider is the person most qualified to evaluate your student’s measurements in conjunction with the child’s other health profile traits and to make recommendations for addressing health risks if they exist.
For more information on Body Mass Index and health, log on to the web site for the Centers for Disease Control and Prevention, US Department of Health and Human Services at www.cdc.gov/growthcharts.
After BMI is calculated for children and teens, the BMI number is plotted on the CDC BMI-for-age growth charts (for either girls or boys) to obtain a percentile ranking. Percentiles are the most commonly used indicator to assess the size and growth patterns of individual children in the United States. The percentile indicates the relative position of the child's BMI number among children of the same sex and age. The growth charts show the weight status categories used with children and teens (underweight, healthy weight, overweight, and obese).
BMI-for-age weight status categories and the corresponding percentiles are shown in the following table.
Weight Status Category
Less than the 5th percentile
5th percentile to less than the 85th percentile
85th to less than the 95th percentile
Equal to or greater than the 95th percentile
BMI is used as a screening tool to identify possible weight problems for children. CDC and the American Academy of Pediatrics (AAP) recommend the use of BMI to screen for overweight and obesity in children beginning at 2 years old.
For children, BMI is used to screen for obesity, overweight, healthy weight, or underweight. However, BMI is not a diagnostic tool. For example, a child may have a high BMI for age and sex, but to determine if excess fat is a problem, a health care provider would need to perform further assessments. These assessments might include skinfold thickness measurements, evaluations of diet, physical activity, family history, and other appropriate health screenings.