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\nBody mass index (BMI) is a person\u2019s weight in kilograms divided by the square of height in meters. It is an inexpensive and easy way to screen for weight categories that may lead to health problems. For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age.
\nRegardless of the current BMI-for-age category, help your child or teen develop healthy weight habits and talk with your doctor or other healthcare provider as part of ongoing tracking of BMI-for-age. If your child has significant weight loss or gain, he or she should be referred to and guided by a doctor or other healthcare provider.
\nTracking growth patterns over time can help you make sure your child is achieving or maintaining a healthy weight. A single BMI-for-age calculation is not enough to evaluate long-term weight status because your child\u2019s height and weight will change as they grow. With individuals, health care providers should consider BMI along with other factors such as family history, blood pressure, blood sugar levels, and eating patterns and physical activity level.
\nObesity during childhood can harm the body in a variety of ways, now and in the future. Learn more about the health consequences of obesity for children.
\nTo help reduce the health risks associated with having obesity during childhood, encourage children and teens to practice healthy habits by:
\nFor more information, see Tips to Promote Healthy Eating and Physical Activity for Children and Teens.
\nCalculating BMI using the BMI Percentile Calculator involves the following steps:
\nAfter BMI is calculated for children and teens, it is expressed as a percentile obtained from either a graph for boys [PDF-62.4KB] and girls [PDF-67.9KB] or a percentile calculator. These percentiles express a child\u2019s BMI relative to US children who participated in national surveys from 1963-65 to 1988-944. Weight and height change during children\u2019s growth and development, as does their relation to body fatness. Consequently, a child\u2019s BMI must be interpreted relative to other children of the same sex and age.
\nThe BMI-for-age percentile 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.
\nWeight Status Category | \nPercentile Range | \n
Underweight | \nLess than the 5th percentile | \n
Healthy Weight | \n5th percentile to less than the 85th percentile | \n
Overweight | \n85th to less than the 95th percentile | \n
Obesity | \nEqual to or greater than the 95th percentile | \n
The following is an example of how sample BMI numbers would be interpreted for a 10-year-old boy.
\nThe CDC BMI-for-age growth charts are available at: CDC Growth Charts: United States.
\nFor children and teens, BMI screens for potential weight and health-related issues. If children or teens have a high BMI for their age and sex, a health care provider may perform further assessments such as skinfold thickness measurements, and evaluations of family history, eating patterns, and physical activity. The American Academy of Pediatrics recommends using BMI to screen for overweight and obesity in children beginning at 2 years old. For children under the age of 2 years old, consult the World Health Organization (WHO) standards.
\nChildren and teen\u2019s BMI-for-age should be checked at least once a year, but a healthcare provider may check it more often. Tracking growth patterns over time can help make sure a child or teen is achieving or maintaining a healthy weight. A single BMI-for-age calculation is not enough to evaluate long-term weight status because children and teen\u2019s height and weight will change as they grow.
\nBMI is interpreted differently for children and teens even though it is calculated with the same formula. Due to changes in weight and height with age, as well as their relation to body fatness, BMI levels among children and teens are expressed relative to other children of the same sex and age. These percentiles are calculated from the CDC growth charts, which were based on national survey data collected from 1963-65 to 1988-944.
\nObesity is defined as a BMI at or above the 95th percentile for children and teens 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 to have obesity. This means that the child\u2019s BMI is greater than the BMI of 95% of 10-year-old boys in the reference population.
\nAccess the CDC Growth Charts.
\nFor adults, BMI is interpreted as weight status categories that are not dependent on sex or age. Read more: How to interpret BMI for adult BMI
\nFor children and teens, healthy weight status is based on BMI between the 5th and 85th percentile on the CDC growth charts. It is difficult to provide healthy weight ranges for children and teens because the interpretation of BMI depends on weight, height, age, and sex. For adults, the interpretation of BMI depends only on height and weight.
\nOverweight is defined as a BMI in the 85th to less than the 95th percentile. Obesity is defined as a BMI at or above the 95th percentile for children and teens of the same age and sex.
\nFor information on helping children maintain a healthy weight, see Tips for Parents \u2013 Ideas and Tips to Help Prevent Childhood Obesity.
\nPeople 20 years old and older should use the Adult BMI Calculator. The adult calculator provides only the BMI value and not the BMI percentile. Consequently, it is not appropriate to use the adult BMI calculator to assess the BMI of children and teens.
\nThe interpretation of BMI varies by age and sex. So, if the children are not the same age and the same sex, the interpretation of BMI has different meanings.
\nSee the following illustration for a 10-year-old boy and a 15-year-old boy who both have a BMI-for-age of 23. (Note that two children of different ages are plotted on the same growth chart to illustrate a point. Normally the measurement for only one child is plotted on a growth chart.)
\nAthletes may have a high BMI because of increased muscularity rather than increased body fatness. A trained healthcare provider can perform appropriate health assessments to evaluate an individual\u2019s health status and risks. Because no single body fat measure clearly distinguishes health from disease or identifies risk of disease, BMI should serve as the initial screening. Other factors, such as fat distribution, genetics, diet, and fitness level contribute to an individual\u2019s disease risk.
\n1Garrow, J.S. & Webster, J., 1985. Quetelet\u2019s index (W/H2) as a measure of fatness. Int. J. Obes., 9(2), pp.147\u2013153.
\n2Freedman, D.S., Horlick, M. & Berenson, G.S., 2013. A comparison of the Slaughter skinfold-thickness equations and BMI in predicting body fatness and cardiovascular disease risk factor levels in children. Am. J. Clin. Nutr., 98(6), pp.1417\u201324.
\n3Wohlfahrt-Veje, C. et al., 2014. Body fat throughout childhood in 2647 healthy Danish children: agreement of BMI, waist circumference, skinfolds with dual X-ray absorptiometry. Eur. J. Clin. Nutr., 68(6), pp.664\u201370.
\n4Kuczmarski, R.J. et al., 2002. 2000 CDC Growth Charts for the United States: methods and development. Vital Health Stat. 11., 11(246), pp.1\u2013190.
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