Body Mass Index vs. Weight -- Which Is More Important? | Parenting

There was a time when parents and pediatricians worried about their babies being too skinny. “Failure to thrive” was a common diagnosis that meant a baby or child was not growing or gaining enough weight. While we still worry about “failure to thrive”, we tend to worry more about babies and children who are perhaps thriving a little too much. Obesity has become a worldwide epidemic even in some of the third world nations.

So how can a parent monitor her child’s growth and be sure he is not overweight? At well baby visits most pediatricians will review the child’s growth by measuring height, weight, and sometimes weight for height. These measurements are plotted on growth curves. Growth curves are standardized charts that allow height and weight measurements of an individual child to be plotted against that of an average of children from similar demographic backgrounds. It is not a perfect comparison but can give the doctor and parents some sense of how their child compares to other U.S. children at that age. The “y” axis is the height or weight measurement and the “x” axis is the age of the child. So, for example if your child is twenty pounds at fifteen months he may be in the fiftieth percentile for weight, meaning he weighs about average. If he is in the seventieth percentile for height or weight, then he is taller or heavier than seventy percent of other children his age, or only thirty percent of children his age are taller or heavier. Weight for height is a percentile that gives another parameter for assessing body size: the larger the number the heavier the child relative to height.

After age two years a 4^th measurement can be added to the mix to give another view of body mass. The BMI or body mass index is a calculation that gives a better sense of whether your child is overweight. If your child’s BMI falls between 25 to 30, he is considered overweight, and if greater than 30, he is obese. However, muscle mass can skew these numbers, and your pediatrician can make a better assessment of whether these numbers are accurate by doing a physical exam. Many children have strong muscular bodies with BMI’s over or close to 25, but they are not overweight.

Most parents can tell if their child is becoming a little chubby unless they are in denial or if they have body image disorders themselves. These measurements along with frank discussions with your pediatrician can guide you in determining whether any intervention needs to be done. For the most part, if parents focus on offering good healthy food choices to their children and encourage family exercise for an hour a day, their offspring should thrive. Of course, there is a genetic component to obesity and there are medical conditions that may preclude simple solutions to weight problems. Be sure to review your child’s growth charts with your pediatrician at each well child visit so that you know if your child is growing and gaining as he should.