Defining Child BMI Categories

BMI and BMI Categories for Children and Teens

Body mass index (BMI) is an anthropometric index of weight and height that is calculated by dividing a person’s weight (in kilograms) by the square of their height (in meters). Because children and teens are growing, the ranges of height, weight, and BMI vary by age and sex. As a result, BMI values need to be expressed relative to other children of the same sex and age.

The CDC Growth Charts display sex-specific BMI-for-age percentile curves and can be used to monitor the growth of children and teens aged 2-19 years.

BMI categories for children and teens are based on sex- and age-specific BMI percentiles, whereas BMI categories for adults are based on BMI only. Child BMI categories and their corresponding sex- and age-specific BMI percentiles are in the following table:

BMI-for-age weight status categories and the corresponding percentiles 
BMI 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

For example, a 10-year-old boy who is 54.5 inches tall (50th percentile for height) and weighs 96 pounds would have a BMI of 22.5 kg/m2, placing him at the 96th percentile for his age and sex, which is in the obesity category.  This means that the boy’s BMI is greater than the BMIs of 96% of 10-year-old boys in the reference population.

An expanded definition of severe obesity is used by the American Academy of Pediatrics (AAP)1:

  • Class 2 Obesity: BMI ≥120% to <140% of the 95th percentile or BMI ≥35 to <40 kg/m2
  • Class 3 Obesity: BMI ≥140% of the 95th percentile or BMI ≥40 kg/m2

For example, a 15-year-old girl who is 63.7 inches tall (50th percentile for height) and weighs 210 pounds would have a BMI of 36.4 kg/m2, placing her at the 99th percentile for her age and sex. Her BMI is 129% of the 95th percentile, which is class 2 obesity based on the expanded definition of severe obesity.

Having a high BMI-for-age percentile is associated with clinical risk factors for cardiovascular disease, including high cholesterol and high blood pressure3, and other chronic conditions. In 2023, the AAP released the Clinical Practice Guideline for the Evaluation and Treatment of Children and Adolescents With Obesity2 to inform pediatric healthcare providers about the standard of care for youth with overweight and obesity and related comorbidities.

  1. Hampl SE, Hassink SG, Skinner AC, et al. Clinical practice guideline for the evaluation and treatment of children and adolescents with obesity. Pediatrics 2023 Feb 1;151(2):e2022060640.
  2. Skinner AC, Perrin EM, Moss LA, et al. Cardiometabolic risks and severity of obesity in children and young adults. NEJM 2015 Oct;373(14):1307-1317. doi: 10.1056/NEJMoa1502821
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