What Is a Normal BMI for Children?

Two overweight children are watching the TV.
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Many children today live at an unhealthy weight. More than 12 percent of children aged 2 to 5 years have obesity, as are 17 percent of children aged 6 to 19, according to the Centers of Disease Control and Prevention (CDC). Obesity increases a child's risk of emotional and physical health problems. Understanding your child's BMI can help prevent her from encountering health disorders.


Charting and Comparing BMI

Body mass index is a calculation of child's weight in relation to her height used to assess body fat and potential weight problems. This number alone is not diagnostic for children. Comparing BMI to other children of the same sex and age in growth charts helps to present a picture of your child's weight. To get the best picture of a child's growth, her growth needs to be charted for some time. A smooth growth curve as a child ages reflects healthy growth.


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Calculating Your Child's BMI

To determine your child's BMI you need to divide her weight in pounds by her height in inches. Then divide this number by her height in inches again. Finally, multiply this number by 703. The answer reflects your child's BMI. The CDC recommends that after completing the BMI calculation, compare it to a BMI percentile chart based on your child's age and sex. A healthy BMI percentile lies between the 5th percentile and the 85th percentile. Anything below this, classifies your child as underweight. Percentiles over this classifies your child as having overweight or obesity. If you find your child's BMI percentile does not fall in the healthy range, contact your child's doctor for further evaluation.


Understanding the Numbers

BMI numbers have different meanings for children of different ages and different sexes. A 10-year-old boy with a BMI of 23 is classified as having obesity, whereas a 15-year-old boy with the same BMI is healthy. Therefore, simply calculating the BMI does not yield a reliable result. The BMI must be compared against age and sex growth charts. The reason for these differences lies in the fact that children develop more muscle as they age and that boys tend to have more muscle than girls. Normal BMIs for boys range from 13.8-16.8 for a 5 year old, 14.2 to 19.4 for a 10 year old, and 16.5-23.4 for a 15 year old. Normal girl BMIs include 13.6 to 16.7 for a 5 year old, 14 to 19.5 for a 10 year old, and 16.3 to 24 for a 15 year old.


Know the Disease Risks

Having a high BMI percentile increases a child's risk for various health conditions, including high blood pressure, cardiovascular disease, asthma, Type 2 Diabetes and sleep apnea. Children with a high BMI are also at risk for developing low self-esteem, behavioral problems and depression. Paying attention to the types of foods eaten, portion sizes and physical activity sets the groundwork for your child's health.


Pay Attention to Low Numbers

Don't ignore a low BMI number. Low BMI percentiles can indicate health problems as well, including malnutrition, which can lead to a weakened immune system, decreased rate of growth, increased risk of injury and increased risk of respiratory problems.



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