Body Mass Index (BMI)

You hear about it at the pediatrician’s office, read about it in media, and maybe even see your child’s school send home a “report card” for it. Your children asks what it all means, and the various numbers and acronyms may confuse you as well as them. What do you say, and just what exactly is, BMI? Here are a few facts about what it is, and why it’s important…

WHAT IS BMI?

BMI stands for “Body Mass Index.” BMI is calculated using a person’s height, weight, age, and gender. The American Academy of Pediatrics (AAP) recommends the use of BMI as a screening tool to identify possible weight problems in children and teens aged 2–19 years.

WHAT IS BMI FOR AGE?

Many schools use BMI “scorecards” to inform parents of their child’s weight, so weight and weight-related issues can be proactively addressed. These scorecards typically use BMI-for-age, which is a percentile that indicates the relative position of the child’s BMI among children of the same age and gender. The percentile corresponds to a weight status category (underweight, healthy weight, overweight and obese). These categories and their corresponding percentiles are shown in this table:

BMI does not measure body fat directly, so a child who has high body muscle and low body fat — such as many athletes — can have a high BMI level. For practical purposes, however, BMI is a reliable way to evaluate a child’s weight.

WHY IS A HIGH BMI CONCERNING?

A high BMI can increase a child’s chances of developing high blood pressure, high cholesterol, and Type 2 diabetes. These problems can occur during childhood, or they may develop as a child grows into adulthood. If a child has obesity, he or she has a higher risk of continuing to have weight problems into adulthood.

WHAT TO SAY

If your child is identified as having a high BMI, either by a health care professional or from a school report, this can be confusing to both the child and parents. And conversations about weight can be difficult to have. What’s important for children to understand is that BMI is a way of measuring health, and that carrying too much weight can hurt health. Parents may also explain to children that having extra weight means their body has to work harder than it needs to. Carrying extra weight isn’t about looks; it’s about health and how it feels. Empathize with your child that there are a lot of barriers to making healthy choices, while assuring him or her that it’s important to make changes, and that you will make these changes together.

WHAT TO DO

Dieting is not encouraged. Diets are often not healthy and can result in unhealthy eating behaviors, including disordered eating. Positive lifestyle changes, however — such as increasing the number of minutes of daily physical activity, limiting sweet foods and beverages, increasing outdoor play time and family play time, and increasing the amount of fruits and vegetables you eat — can all have a positive impact on a child’s weight and overall health. Consider that children are more successful when the entire family makes changes together.

Ask your pediatrician about your child’s BMI, whether it is considered to be in the healthy range, and what you can do to help your child maintain a healthy weight.

Anne Marie Kuchera, our Kids Plus Nutrition Consultant, is a Licensed Professional Counselor and Registered Dietitian.