Body Mass Index (BMI)
What’s the Big Deal About BMI?
Childhood obesity is a national problem begging for our intervention. We know that currently more than 15% of 6 – 19 year olds are at or above the 95th percentile for BMI on a standard growth chart. Studies have shown that a 4 year old who is obese has a 20% chance of becoming an obese adult, with all the associated health problems, but that chance rises to 80% if a child is obese at 14 years of age. So, it is clear that early prevention can be extremely effective. As a result, many public school systems have begun identifying “at risk” children by calculating BMIs as a routine screening practice, and physicians are being encouraged to track children’s BMIs beginning at 3 years of age in an effort to promote healthier lifestyle habits early. We will calculate your child’s BMI at every Well-Child Visit starting at age 3 so we identify those children at risk.
The body mass index, or BMI, is simply a calculation that compares the weight of a child with their height. It is widely used to define the terms “overweight” and “obese” because it correlates well with more accurate measures of body fatness and is easily obtained from routinely measured height/weight/age data. So if your child has a BMI between the 85th and 95th percentile for their age and gender, they are considered “at risk” for becoming overweight while a child with a BMI at or above the 95th percentile is considered overweight or obese. Similarly, children at the other end of the BMI chart are considered underweight if their BMI is at or below the 5th percentile. However, the BMI is only a statistical approximation and clinical judgment must be used in applying these criteria to a specific patient. There is a wide range of “normal” for the BMI, and school nurses are being trained to identify those students who MAY BE at risk. Factors like activity level and genetics play major roles in determining what is “normal” for an individual child.
It is for this reason that the BMI should never be interpreted without additional information, including lifestyle habits (dietary habits, exercise habits, sedentary activities), existing medical conditions, and growth trends over time. Ultimately, studying your children’s body mass index is not just about making them “thinner.” It is about creating a lifetime of healthy eating and exercise habits, so they can become healthy adults.
If you still have concerns about your child’s BMI, here are some helpful tips. Good luck and good health!