Do you wonder if your child is growing appropriately? If his or her body weight is appropriate for his or her height? Do you worry that he or she may be gaining too much weight?
One of the best ways to keep track of your child’s growth is to follow the Body Mass Index (BMI) during growth. Your pediatrician will use this tracking tool, displayed as a growth chart, to assess your child’s growth when you visit for routine checkups.
Your child’s BMI is determined from a calculation that includes your child’s own weight compared to height. To calculate BMI, your child’s weight is divided by his or her height using a complex calculation. From that result, a body mass index (BMI) percentile is determined. This BMI percentile is compared to a set of standards for a child’s age and sex.
The BMI percentile reflects your child’s growth in comparison to other children of the same age and gender. The weight status categories are: underweight, healthy weight, overweight, and obese.
|Underweight||< 5th percentile|
|Healthy weight||5th percentile to less than the 85th percentile|
|Overweight||85th percentile to less than the 95th percentile|
|Obese||> 95th percentile|
It’s important to understand that children grow differently from adults: the amount of body fat changes in childhood, and girls tend to have more body fat than boys, especially as children enter puberty. Since growth is evolving throughout childhood, the BMI values for a healthy weight change as children grow. That is why it’s difficult to give a broad “healthy” weight range for all children—a healthy weight is individualized to the child.
The BMI score for your child is best used as a tracking tool to monitor his or her growth over time and to screen for problems such as being overweight and obesity. Because infants and very young children are at a unique period of accelerated growth, the American Academy of Pediatrics (AAP) recommends using the BMI values beginning at two years of age and continuously throughout childhood.
One limiting factor about the BMI is that it assesses total weight and does not differentiate between fat, muscle, and bone. So, if you have a stocky boy, his BMI may indicate an overweight status, but he may just have more muscle and heavy bones. Because of this, if your child is found to have a high BMI, further evaluation, including dietary patterns, activity level, and assessment of body fatness, should occur to determine if excess weight is a problem.
Reviewed by Dr. Sara Connolly, September 2020
- The BMI is a way to evaluate your child’s overall growth.
- Keep track of your child’s BMI over time to pick up on any deviations in growth.
- BMI does not differentiate between fat, muscle, and bone.