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Defining Childhood Obesity

BMI for Children and Teens

Body mass index (BMI) is a measure used to determine childhood overweight and obesity. Overweight is defined as a BMI at or above the 85th percentile and below the 95th percentile for children and teens of the same age and sex. Obesity is defined as a BMI at or above the 95th percentile for children and teens of the same age and sex.

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 determined using an age- and sex-specific percentile for BMI rather than the BMI categories used for adults. This is because 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 obese. This means that the child’s BMI is greater than the BMI of 95% of 10-year-old boys in the reference population.

The CDC Growth Charts are the most commonly used indicator 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 were based on expert committee recommendations and are shown in the following table.

Weight Status Category Percentile Range
Underweight Less than the 5th percentile
Normal or Healthy Weight 5th percentile to less than the 85th percentile
Overweight 85th to less than the 95th percentile
Obese 95th percentile or greater

BMI does not measure body fat directly, but research has shown that 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 an alternative to direct measures of body fat. A trained healthcare provider should perform appropriate health assessments in order 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. Freedman DS, Mei Z, Srinivasan SR, Berenson GS, Dietz WH. Cardiovascular risk factors and excess adiposity among overweight children and adolescents: the Bogalusa Heart Study. J Pediatr. 2007;150(1):12—17.e2.
  3. Whitlock EP, Williams SB, Gold R, Smith PR, Shipman SA. Screening and interventions for childhood overweight: a summary of evidence for the US Preventive Services Task Force. Pediatrics. 2005;116(1):e125—144.
  4. Han JC, Lawlor DA, Kimm SY. Childhood obesity. Lancet. May 15 2010;375(9727):1737—1748.
  5. Sutherland ER. Obesity and asthma. Immunol Allergy Clin North Am. 2008;28(3):589—602, ix.
  6. Taylor ED, Theim KR, Mirch MC, et al. Orthopedic complications of overweight in children and adolescents. Pediatrics. Jun 2006;117(6):2167—2174.
  7. Dietz W. Health consequences of obesity in youth: Childhood predictors of adult disease. Pediatrics 1998;101:518—525.
  8. Swartz MB and Puhl R. Childhood obesity: a societal problem to solve. Obesity Reviews 2003; 4(1):57—71.
  9. Biro FM, Wien M. Childhood obesity and adult morbidities. Am J Clin Nutr. May 2010;91(5):1499S—1505S.
  10. Whitaker RC, Wright JA, Pepe MS, Seidel KD, Dietz WH. Predicting obesity in young adulthood from childhood and parental obesity. N Engl J Med 1997;37(13):869—873.
  11. Serdula MK, Ivery D, Coates RJ, Freedman DS. Williamson DF. Byers T. Do obese children become obese adults? A review of the literature. Prev Med 1993;22:167—177.
  12. National Institutes of Health. Clinical Guidelines on the Identification, Evaluation, and Treatment of Overweight and Obesity in Adults: the Evidence Report. Bethesda, MD: National Institutes of Health, U.S. Department of Health and Human Services; 1998.
  13. Freedman DS, Khan LK, Dietz WH, Srinivasan SR, Berenson GS. Relationship of childhood overweight to coronary heart disease risk factors in adulthood: The Bogalusa Heart Study. Pediatrics 2001;108:712—718.