Overweight and Obesity Definitions

Body mass index (BMI) – a reliable indicator of excess body fat for most children, adolescents, and adults – is used to classify someone as underweight, at a healthy weight, overweight, or obese. For children and adolescents, BMI is compared to growth charts that show BMIs for different ages and genders.

BMI is calculated from an individual’s height and weight using the following formula:
BMI (kg/m2) = [weight in pounds / (height in inches x height in inches)] x 703

BMI Classifications for Adults:

  • Underweight: BMI < 18.5 kg/m2
  • Healthy weight: BMI 18.5-24.9 kg/m2
  • Overweight: BMI 25.0-29.9 kg/m2
  • Obese: BMI >/= 30 kg/m2

BMI Classifications for Children and Adolescents:

  • Underweight: BMI-for-age < 5th percentile
  • Healthy weight: BMI-for-age >/= 5th percentile to < 85th percentile
  • Overweight: BMI-for-age >/= 85th percentile to < 95th percentile
  • Obese: BMI-for-age >/= 95th percentile