Body mass index (BMI) is one tool widely used to determine if a child is at a healthy normal weight. BMI uses height and weight to determine how the child compares to the general child population. BMI for children and teens is sometimes referred to as BMI-for-age.
Significance
Maintaining a healthy weight is one way to combat many diseases and health concerns. BMI is an easy way to determine if children are on track with their weight or if they need to make modifications in exercise and diet habits io get to a normal weight and healthy BMI to avoid health problems.
Benefits
BMI is an easy, pain-free way to determine if a child is facing weight based health risks. BMI is inexpensive and takes little time to calculate, making it a first choice among pediatricians and health care providers. The Centers for Disease Control and Prevention (CDC) and the American Academy of Pediatrics (AAP) recommend using BMI for children aged 2 to 18 to screen for those overweight and for obesity.
Calculations
Obtain the child or teen's accurate height and weight. Calculate the BMI by dividing weight in pounds by height in inches, squared, and multiply by a conversion factor of 703. The formula reads as follows: weight (lbs.) / [height (inches)]2 x 703. Insert the child or teen's height and weight information into the formula to yield her BMI results. Take this BMI number and plot it on the CDC BMI-for-age growth charts to get a percentile for the child or teen.
Interpretation
According to the CDC, the BMI-for-age percentile is used to interpret the BMI number because BMI is both age- and sex-specific for children and teens. These criteria are different from those used to interpret BMI for adults. Age and sex are considered for children and teens because body fat changes with age and differs between boys and girls. If the child percentile is less than 5 percent, that child is considered to be underweight. A healthy, normal weight is considered to fall between the 5th and 85th percentile. The 85th to 95th percentile is considered overweight and anything above the 95th percentile falls into the obese category.
Considerations
It is possible for two children to have the same BMI number, but if they are not the same sex and the same age, the BMI numbers have different meanings. The calculated numbers will fall into different percentiles when graphed on the correct BMI-for-age chart because there are differences in age and in sex.
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