How is BMI used with children and teens?
Girls and boys develop differently and have different amounts of body fat at different ages, so a child's age is taken into consideration when looking at their BMI. For children and teens, BMI age- and sex-specific percentiles are used.
The interpretation of BMI is both age- and sex-specific for children and teens. BMI-for-age growth charts take into account these differences and allow translation of a BMI number into a percentile for a child's sex and age.2
Nearly 1 in 3 children or teens in the US are overweight or obese. Carrying extra weight as a child or teenager can pose significant health risks, both during childhood and into adulthood.14
Maintaining a healthy weight during childhood is especially important for heart health. Research shows that nearly 60% of overweight children aged 5-17 had at least one risk factor for cardiovascular disease and 25% had two or more. Also, obese children have an 80% chance of staying obese their entire lives.
Heart disease, often caused by high blood pressure or high cholesterol, is not the only health risk of obesity. Childhood obesity may also lead to significant health problems, including:
- Type 2 diabetes
- Sleep apnea
- Psychological stress, including low self-esteem, caused by the social stigma of being obese.
How to calculate BMI for children and teens
BMI for children and teens is worked out the same way as for adults. However, the BMI number and age then needs to be located on a sex-specific BMI-for-age chart to indicate whether the child is within a healthy range.
BMI-for-age chart by CDC for boys and girls 2-20 years
BMI-for-age charts are recommended to assess weight in relation to stature for children ages 2-20 years.
Full PDF versions: boys | girls
Classification of percentiles for children over age 2, or teens:
|Weight status category||Percentile range|
|Underweight||Less than the 5th percentile|
|Healthy weight||5th percentile to less than the 85th percentile|
|Overweight||85th to less than the 95th percentile|
|Obese||Equal to or greater than the 95th percentile|
Alternatively, the CDC has a calculator that provides BMI and the corresponding BMI-for-age percentile on a CDC BMI-for-age growth chart.
Although BMI is used to screen for overweight and obesity in children and teens, BMI is not a diagnostic tool.15
A child may have a high BMI for age and sex, but to determine if excess fat is a problem, a health care provider would need to perform further assessments. These assessments might include skinfold thickness measurements, evaluations of diet, physical activity, family history and other appropriate health screenings.
Healthy weight ranges cannot be provided for children and teens for the following reasons:
- Healthy weight ranges change with each month of age for each sex
- Healthy weight ranges change as height increases.
Health consequences of overweight and obese adults
The BMI ranges are based on the relationship between body weight and disease and death. Overweight and obese individuals are at increased risk for many diseases and health conditions, including the following:2
Overweight and obese people have a higher risk of various diseases including coronary heart disease.
- Dyslipidemia (for example, high LDL cholesterol, low HDL cholesterol, or high levels of triglycerides)
- Type 2 diabetes
- Coronary heart disease
- Gallbladder disease
- Sleep apnea and respiratory problems
- Some cancers (endometrial, breast and colon).
On the next page we look at the limitations of BMI and the controversy surrounding it.