Should I worry about my child's BMI? Body mass index explained

Does your doctor say your child's body mass index (BMI) puts them in the overweight category, but you think they look healthy? BMI measurements can cause a lot of frustration and confusion for parents.

"Developing healthy habits at an early age is crucial as children grow and develop," says Bethany Cartwright, M.D., a pediatric endocrinologist at Children's Health℠. "Children with a BMI over the 85th percentile have a greater likelihood to have obesity as an adult, placing them at risk for future health complications."

What does BMI mean?

It is hard to tell whether a child has overweight or obesity just by looking at them. Body mass index, or BMI, is a ratio of height and weight that is the easiest way to estimate excess weight in most children and teens.

Since the normal body fat of a child changes as he or she ages, your child's status is found using categories that are age- and sex-specific. See the BMI calculator for children and teens.

What are the risks of an elevated BMI?

Having an elevated BMI can increase the risk of developing type 2 diabetes, heart disease and high blood pressure.

"While I hope all children feel comfortable and confident in their bodies no matter their size, we do need to be watchful for children who are at risk of significant disease in their teenage or adult years so that we can provide extra help with avoiding these complications," says Dr. Cartwright who is board-certified by the American Board of Obesity Medicine.

After a child's BMI is calculated, it is measured against standardized values for other children of the same sex and age to get a general picture of how their BMI compares. The 85th percentile is the American Academy of Pediatrics' recommended cutoff for signaling a concern of excess weight.

BMI and weight categories

A child's BMI percentile will place them in one of the following categories:

• Underweight
  • Percentile Range: Less than the 5^th percentile
• Healthy weight
  • Percentile Range: 5th percentile to less than the 85^th percentile
• Overweight
  • Percentile Range: 85^th to less than the 95^th percentile
• Obesity
  • Percentile Range: Equal to or greater than the 95^th percentile
• Severe Obesity
  • Percentile Range: Equal to or greater than the 120% of the 95^th percentile

The most important thing to know about the BMI is that it is a screening tool to identify potential weight problems, not a diagnosis. To diagnose a child as overweight or obese, your physician will take many other health factors into account.

"The BMI number isn't perfect, and it doesn't take into account things like heavy muscularity" says Dr. Cartwright, "But it is often our first warning signal – especially if we see it climbing rapidly."

If you are concerned about your child's weight, be patient and focus on small, steady changes toward a healthier lifestyle. "Every small step, whether in terms of nutrition or physical activity, will make your body healthier, no matter what the number on the scale does," says Dr. Cartwright. It is best to track weight and BMI with your doctor over time, because as your child grows, their body proportions will change along with their BMI.

It is best to avoid using weight-related terms like overweight and obesity with children, and instead focus on healthy behaviors. Learn more tips about speaking to your child about weight. If you are concerned about how to help your child eat healthy, speak to your physician about resources and appropriate strategies.

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Interested in learning more about healthier habits for your family? Read more about pediatric weight management programs that include Get Up & Go, COACH, bariatrics and nutrition clinics.