This number is then compared to other U.S. children of the same age and sex to determine what's called a BMI percentile. For example, a BMI-for-age percentile of 65 means that the child's weight is greater than that of 65% of other children of the same age and sex. Pediatricians plot this number on a
standardized growth chart for a visual comparison, and to help track growth trends over time.
The best way to know your child's BMI is to have your child's pediatrician measure and discuss the results with you. Your pediatrician can advise you on ways to strategies that focus on developing and supporting healthy habits at home.
What are BMI percentile categories?
The terms underweight, healthy weight, overweight, and obese can be another source of confusion for many parents. For pediatricians, these are useful categories that can show whether a child is gaining weight too quickly or not quickly enough.
What does your child's BMI mean?
To find out which category a child is in, pediatricians will use both the BMI number and its corresponding percentile.
For example, a 5-year-old boy with a BMI in the 88th percentile means this child's BMI is higher than 88% of other 5-year-old boys and would be considered in the overweight category. The BMI percentile-ranges and weight status categories:
BMI percentile range
Less than 5th percentile
5th to 84th percentile
85th to 95th percentile
Above 95% percentile
BMI: understanding the numbers
Ideally, children should fall in the target ranges between the 5th and 85th percentiles. Children below 5th percentile could have a nutritional shortfall—either not taking in enough calories or burning up more calories than they are getting, or both. Likewise, children above the 85th percentile are likely, but not always, getting too many calories in their diet, not burning up enough calories through physical activity, or both. Although less common, some medical conditions can cause children to gain or lose weight more easily.
Just one piece of the health puzzle
A child's BMI is a valuable screening tool, but it's only one piece of the puzzle to finding out if a child is at a healthy weight. First, it is important to know that BMI is not a perfect measurement. For example, shorter children with a muscular build may have a high BMI but little body fat. In general, BMI percentiles higher than 95% are a reliable sign that a child has excess body fat and is at risk for health complications.
Second, it is especially important to not focus solely on specific numbers but rather, using the BMI along with making healthy choices. It is entirely possible to have a BMI in the healthy range but routinely make poor health decisions (eating junk food and not exercising). Likewise, it is also possible to have a BMI in the overweight or obese category while making regular healthy choices.
Preventing obesity and keeping BMI in the healthy range is critical for children's overall health and well-being, as well as continued health as they grow and become adults. Talk with your pediatrician if you have any concerns about your child's weight.
About Dr. Kirkilas
Gary Kirkilas, DO, FAAP, is a general pediatrician at Phoenix Children's Hospital with a unique practice. His office is a 40-foot mobile medical unit that travels to various homeless shelters in Phoenix providing free medical care to families. He and his lovely wife, Mary (a pediatric emergency doctor), have three wonderful (most of the time) children and two dachshunds.