Defining Childhood Weight Status

BMI for Children and Teens

Body mass index (BMI) is commonly used to determine childhood weight status. BMI is calculated by dividing a person’s weight in kilograms by the square of height in meters. For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age.

A child’s weight status is different from adult BMI categories. Children’s body composition varies as they age and varies between boys and girls. Therefore, BMI levels among children and teens need to be expressed relative to other children of the same age and sex.

For example, a 10-year-old boy of average height (56 inches) who weighs 102 pounds would have a BMI of 22.9 kg/m2. This would place the boy in the 95th percentile for BMI, and he would be considered as having obesity. This means that the child’s BMI is greater than the BMI of 95% of 10-year-old boys in the reference population.

CDC Growth Charts are commonly used to measure the size and growth patterns of children and teens in the United States. BMI-for-age weight status categories and the corresponding percentiles, based on expert committee recommendations, and are in the following table:

BMI-for-age weight status categories and the corresponding percentiles 
Weight Status Category BMI Range
Underweight Less than the 5th percentile
Healthy Weight 5th percentile to less than the 85th percentile
Overweight 85th percentile to less than the 95th percentile
Obesity 95th percentile or greater
Severe Obesity 120% of the 95th percentile or greater OR 35 kg/m2 or greater

In children, BMI percentile cutoffs for obesity are intended to reliably define a level above which a child is more likely to have or be at risk of developing obesity-associated adverse health outcomes or diseases. For more information, see a resource guide assessing childhood obesity.

BMI does not measure body fat directly, but BMI is correlated with more direct measures of body fat, such as skinfold thickness measurements, bioelectrical impedance, densitometry (underwater weighing), dual energy x-ray absorptiometry (DXA) and other methods1,2,3. BMI can be considered a practical alternative to direct measures of body fat. A trained healthcare provider should perform appropriate health assessments to evaluate an individual’s health status and risks.

  1. Barlow SE and the Expert Committee. Expert committee recommendations regarding the prevention, assessment, and treatment of child and adolescent overweight and obesity: summary report. Pediatrics 2007;120 Supplement December 2007:S164—S192.
  2. Cote AT, Harris KC, Panagiotopoulos C, et al. Childhood obesity and cardiovascular dysfunction. J Am Coll Cardiol 2013; 62 (15):1309–1319.
  3. US Preventive Services Task Force. Screening for Obesity in Children and Adolescents: US Preventive Services Task Force Recommendation Statement. JAMA. 2017 Jun 20;317(23):2417-2426. doi: 10.1001/jama.2017.6803.
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