Defining Childhood Overweight and Obesity

Body mass index (BMI) is a practical measure used to determine overweight and obesity. BMI is a measure of weight in relation to height that is used to determine weight status. BMI can be calculated using either English or metric units. BMI is the most widely accepted method used to screen for overweight and obesity in children and adolescents because it is relatively easy to obtain the height and weight measurements needed to calculate BMI, measurements are non-invasive and BMI correlates with body fatness.6 While BMI is an accepted screening tool for the initial assessment of body fatness in children and adolescents, it is not a diagnostic measure because BMI is not a direct measure of body fatness.

Use of BMI to Screen for Overweight and Obesity in Children

For children and adolescents (aged 2–19 years), the BMI value is plotted on the CDC growth charts to determine the corresponding BMI-for-age percentile.

• Overweight is defined as a BMI at or above the 85th percentile and lower than the 95th percentile.
• Obesity is defined as a BMI at or above the 95th percentile for children of the same age and sex.

These definitions are based on the 2000 CDC Growth Charts for the United States and expert committee.7 A child's weight status is determined based on an age- and sex-specific percentile for BMI rather than by the BMI categories used for adults. Classifications of overweight and obesity for children and adolescents are age- and sex-specific because children's body composition varies as they age and varies between boys and girls.

For more information, see the About BMI for Children and Teens.

Tips for Parents
What can you do as a parent or guardian to help prevent childhood overweight and obesity? We have some ideas in our Healthy Weight section.

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