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Understanding Childhood Obesity: How BMI Should Be Used to Track Weight



You can take steps at home to help your child get more exercise, spend less time in front of a screen and eat healthier.

Across the U.S., obesity is still a nationwide problem affecting both adults and children. For children, being obese at a young age can lead to other serious health risks, both during childhood and into adulthood.

According to the Centers for Disease Control and Prevention, about one in five American kids between the ages of six and 19 are obese. If you're worried your child could be overweight, there are certain tools like the Body Mass Index (BMI) that can screen for possible weight issues.

“BMI is a good measure of a person’s risk of developing diseases related to being overweight or obese,” says Rima Himelstein, M.D., an adolescent medicine specialist at Crozer Health. “It’s a way to understand if a child or teen is underweight, of a healthy weight, overweight, or obese.”

What is BMI?

BMI is a calculation that uses a person's height and weight measurements to estimate their body fat. It can track weight in both adults and children. It does not measure body fat directly but research shows it can measure body fat better than other methods of measurement.

“BMI is a safe and easy way to perform screenings for a patient’s weight category,” says Dr. Himelstein. “Both in children and adults, it can help screen for potential weight problems that could lead to other health problems.”

Understanding Your Child's BMI

BMI measurements are used differently when tracking a growing child as opposed to an adult. As kids grow, their bodies and body fat levels change. Instead of simply looking at the BMI as a number, the doctor will evaluate the child’s percentile—or how they compare to other children of the same age, gender, and height.

“Boys and girls have different levels of body fat that also change as they grow older or taller,” says Dr. Himelstein. “Age and gender-specific charts are used to evaluate BMI percentiles based on different growth patterns for each gender.”

In each age group, the BMI percentiles will indicate if the child is underweight, at a healthy weight, overweight or obese. A good rule of thumb when evaluating your child’s BMI is to keep these ranges in mind:

  • If they weigh less than the fifth percentile, they are considered underweight.
  • A healthy weight is more than the fifth percentile and less than the 85th percentile.
  • If they are between the 85th and 95th percentile, they are considered overweight.
  • If they are equal to or greater than the 95th percentile, they are considered obese.

It’s important to understand that these are guidelines to help your doctor with an evaluation, and BMI percentile doesn’t automatically mean a child is at risk. For instance, a healthy high school football player may have a BMI above the 95th percentile, but that doesn’t necessarily mean they will develop health problems related to obesity. Doctors will examine all areas of the child’s life and perform additional assessments if necessary.

When Your Child’s BMI Could be Too High

“Talking to your child’s doctor is recommended as the first step if a parent ever has concerns about a child’s health or weight,” says Dr. Himelstein. “Your healthcare provider can look at your child’s BMI, medical history and lifestyle habits to determine if they may have a weight or growth problem.”

Certain steps you can take at home include helping your child get more exercise, spend less time in front of a screen and eat healthier.

No matter what your child’s BMI may be, Dr. Himelstein says it’s always good to focus on the basics. She recommends the 5-2-1-0 plan to her patients:

  • 5: Eat 5 fruits and vegetables every day
  • 2 – Keep recreational screen time to less than 2 hours per day
  • 1 – At least 1 hour of active play every day
  • 0 – 0 sodas and fruit drinks per day

If you feel your child’s BMI may be high for their age, talk to your doctor about your concerns. A doctor will be able to give a proper BMI measurement and help you understand if your child has a weight problem.

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