A note to parents: Childhood obesity and BMI

Despite living in a “thin is in” society, obesity is a significant problem in this country, not only among adults, but children as well. In fact, Michelle Obama decided to take on childhood obesity earlier this year when she began the “Let’s Move!” campaign. As the initiative’s website describes it, “Let’s Move! has an ambitious but important goal: to solve the epidemic of childhood obesity within a generation.”

My hat’s off to the First Lady and I encourage you to find out more about her childhood anti-obesity campaign. That leads me to today’s topic: BMI (body mass index).

You may have used an online BMI calculator to determine your level of body fat. If you’re a parent, you might be tempted to use the same calculator for your child. That would be a mistake.

“For adults, BMI is based on height and weight,” explains Becky Vicars, a registered dietician at Scott & White. “The BMI number for children and adolescents is calculated the same way as it is for adults, but the number is evaluated differently—according to age and gender.”

That’s why the Centers for Disease Control and Prevention (CDC) provide a BMI calculator for adults and a separate BMI calculator for children and teens.

They also explain why age and gender are important when interpreting BMI for children and teens:

  • The amount of body fat changes with age.
  • The amount of body fat differs between girls and boys.

It’s for those two reasons that pediatric growth charts are used for ages two to 20. The charts take those criteria into account and also explain why a BMI of one number may be considered obese for a child of one age, but actually within a normal weight range for a child of another age.

BMI is Just Part of the Health Equation

Whether for a child, teen or adult, “BMI is a calculation used in combination with other health screening tools to determine a person’s risk for developing obesity-associated diseases,” says Vicars. “Although BMI is considered to be a fairly reliable indicator of body fat, it may overestimate body fat in very muscular individuals and it may underestimate body fat in others.” For example, BMI may not be an accurate indicator of body fat for competitive athletes, pregnant or nursing women, and the elderly.

CDC and the American Academy of Pediatrics (AAP) have approved the use of BMI to screen for overweight and obesity in children beginning at age two and continuing through the teen years. The CDC warns, however, that “BMI is not a diagnostic tool. For example, a child may have a high BMI for age and sex, but to determine if excess fat is a problem, a health care provider would need to perform further assessments. These assessments might include skin fold thickness measurements, evaluations of diet, physical activity, family history, and other appropriate health screenings.”

If a high BMI reading has you concerned about a member of your family (or yourself), schedule an appointment with your primary care physician. Taking action now could prevent serious health conditions in the future.

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A note to parents: Childhood obesity and BMI