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The ABC's on BMI

Knowing What Your Child’s Weight Means

It’s important to be at a healthy weight. Body Mass Index—or BMI—and waist size are two numbers that can help you decide if your child’s weight is healthy, or if you need to make some changes. This tip sheet explains how to find both and what they mean.

Body Mass Index (BMI)

BMI is a measure of how much your child weighs compared to how tall she is. Children’s BMIs are also based on their age and gender. In addition to a number, BMI percentiles are also used to determine if your child’s weight is appropriate for his or her height. To find your child’s BMI—and learn what it means for their health—use the U.S. Centers for Disease Control and Prevention’s calculator at

What is a BMI percentile?

Percentiles are the most commonly used indicator to determine the size and growth patterns of children. A BMI is calculated for a child in the same way it is done for adults but the BMI number is plotted on a BMI‐for-age growth chart (for either girls or boys) to obtain a percentile ranking. The growth charts show the weight status categories used with children and teens. BMI‐for‐age weight status categories and percentiles are shown in the following table. For more information about interpretation for children and teens, visit

BMI percentile

How is BMI used with children and teens?

For children and teens, BMI is not a diagnostic tool and is used to screen for potential weight and health-related issues. For example, a child may have a high BMI for their 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. The American Academy of Pediatrics recommends the use of BMI to screen for overweight and obesity in children beginning at 2 years old.

What are the health consequences of obesity during childhood?
Health Risks Resulting from Obesity
​Childhood obesity can have a harmful effect on the body in a variety of ways. They include:
  • 40% of overweight children will continue to have increased weight during adolescence

  • High blood pressure and high cholesterol, which are risk factors for cardiovascular disease (CVD). In one study, 70% of obese children had at least one CVD risk factor, and 39% had two or more.

  • Increased risk of impaired glucose tolerance, insulin resistance and type 2 diabetes.

  • Breathing problems, such as sleep apnea, and asthma.

  • Joint problems and musculoskeletal discomfort.

  • Fatty liver disease, gallstones, and gastro-esophageal reflux (i.e., heartburn).

  • Psychological stress such as depression, behavioral problems, and issues in school.

  • Low self-esteem and low self-reported quality of life.

  • Impaired social, physical, and emotional functioning.

Adult Health Risks:
  • Obese children are more likely to become obese adults. Adult obesity is associated with a number of serious health conditions including heart disease, diabetes, and some cancers.

  • If children are overweight, obesity in adulthood is likely to be more severe.

  • 75−80% of obese adolescents will become obese adults

  • A child with a high BMI has a high risk of being overweight or obese at 35 years of life and this risk increases with age

  • Complications of obesity starting in childhood, such as diabetes, may be more severe in adulthood as the duration of obesity will be longer​

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