Body Mass Index in Children

BMI in Children

Body mass index is an important tool to identify childhood obesity.

Are you worried that your child could be overweight? Nearly 1 in 3 kids or teens in the U.S. are overweight or obese. Carrying extra weight as a child or teenager can pose significant health risks, both during childhood and into adulthood. 

Maintaining a healthy weight during childhood is especially important for heart health.

Research shows that nearly 70% of overweight children had at least one risk factor for cardiovascular disease, and 39% had two or more. Obese adolescents have an 80% chance of staying obese their entire lives.

But heart disease, often caused by high blood pressure and/or high cholesterol, isn’t the only health risk. Childhood obesity may also lead to significant health problems, including:

  • Type 2 diabetes
  • Asthma
  • Sleep apnea
  • Joint problems
  • Gallstones and gallbladder disease
  • Psychological stress, including low self-esteem, anxiety or depression
  • Social and mental health issues caused by bullying and the social stigma of being obese

What is BMI?

BMI is calculated using weight and height measurements and is an estimator of body fat. It is not a direct measurement of fat, but research has shown that BMI measurements correlate to direct measurement. It’s an inexpensive and easy-to-perform way to screen for possible weight. BMI is measured differently in adults than in children, so it is important to use the proper calculator to find out yours and your child’s separately.

BMI is not used to diagnose health issues, but it can be an early screening tool. Your child’s health care professional may use additional information, such as family history, information about diet and exercise or a measurement of skinfold thickness or other tests to determine whether excess fat is a problem.

You can find your child’s BMI by entering their height and weight into this online BMI calculator for children and teens from the Centers for Disease Control.

What does my child’s BMI mean?

For children and teens, BMI is evaluated using age- and sex-specific charts that considers the different growth patterns for the sexes. Weight and the amount of fat in the body differ for boys and girls, and those levels change as they grow taller and older.

These charts help health care professionals determine how a child’s particular BMI reading compares to the readings of other U.S. children their age. The group is divided into percentiles that reflect whether a child is at a healthy weight, underweight, overweight or obese.

Children over age 2, or teens whose BMI is:

  • Less than the 5th percentile are considered underweight.
  • Between the 5th percentile and less than the 85th percentile are at a healthy weight.
  • In the 85th percentile to less than the 95th percentile are considered overweight.
  • Equal to, or greater than the 95th percentile are considered obese.


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