Does body mass index (BMI) matter for children?

BMI matters for all of us.   It is a reliable indicator of body fatness for most children and teens. Knowing your child’s BMI is a great way to know if they need to get moving and get healthy. For children and teens, BMI is age- and sex-specific and is often referred to as BMI-for-age.  Remember, BMI is used as a screening tool for children and is not a diagnostic tool.  A health care provider would need to perform further assessments to determine if your child has a problem.

If your child has an unhealthy BMI, it's time to instill some household changes.  As a parent you need to be aware of what your child puts into their mouth, make good food choices for them and with them, and educate your kids about empty calories (you know those Twinkies that could outlast an atom bomb).  There is no need to have junk food in the house for your kids.  They don’t need it and neither do you.  Also get them moving!  If your child is resistant to exercise, disguise it as a game of tag and the whole family will have fun and burn calories together!

BMI matters for children age 2 – 19 as well as adults.  Physicians use BMI to calculate a number that indicates body fatness.  You may have seen the BMI charts in your pediatrician’s office and had your child’s BMI plotted at their yearly physical. The charts indicates a percentile ranking relative to other children among the same gender and age.  A child is considered to be in the healthy weight category between the 5th and 85th percentile. A child in the overweight category falls greater than the 85th percentile. The BMI is not a perfect measure and it cannot tell you the body fat percentage of your child.  It is used because it correlates well with body fatness and is a simple, non invasive way to screen for overweight in children.

BMI is not as important for children as it for adults.  With adults, you are able to determine your weight class and this may assist in guiding you in the proper direction depending on what your goals may need to be.  Children’s bodies are rapidly changing and BMI should be a reading.  If your child is above the eighty fifth percentile then further medical guidance may be necessary.

At 2 years of age body mass index (BMI) is a measure of healthy weight for children. Obesity is a concern and epidemic in children of developed countries. Children 2 years of age and older at an unhealthy weight may be at risk for premature chronic diseases such as hypertension and heart disease. BMI growth charts are available online from the Center for Disease Control.

I recommend BMI to be interpreted by a healthcare provider such as your pediatrician, registered dietitian or registered nurse. BMI in some rare cases be a false indication of obesity, for example if increased muscle mass is present.

Absolutely! BMI measurements for children are just as important as they are for adults. Because they are going through rapid physiological changes, BMI calculators for children and teens will also take into account age and gender. Check out the calculator at the Centers for Disease Control (CDC) website at http://apps.nccd.cdc.gov/dnpabmi/ for more information.

Body mass index should be used only as a guide for children. For children, BMI is plotted on growth charts that are specific to children's age and gender. These growth charts also allow the pattern of a child's growth from the ages of two to twenty to be traced. Categories for children have been established that approximately correspond to the adult definitions of overweight and obesity. A BMI above the 85th percentile for a child's age and gender places them in the "at risk" category. A BMI above the 95th percentile for a child's age and gender is used to determine childhood obesity. However, BMI for children should only be used as a reference. There are many factors that contribute to potential health risks in children and weight is just one of those. If you think your child may be overweight, help them by becoming a good role model. Encourage the whole family to eat less, choose more nutritious foods, and increase physical activity levels. Being active as a family can also be a great time for family bonding!

The criteria used to interpret the meaning of the BMI number for children and teens are different from those used for adults. For children and teens, BMI age and sex-specific percentiles are used for two reasons:

The amount of body fat changes with age. The amount of body fat differs between girls and boys.

For adults, on the other hand, BMI is interpreted through categories that do not take into account sex or age.

Body Mass Index (BMI) is used with children starting at age two. It is basically a screening tool to determine if other assessments such as skin fold caliper test (body composition) or a deeper examination of diet, lifestyle and family history are necessary. Scoring in the 85th percentile or higher is an indicator that such screening should be performed.