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Ask A Scientist

What percentage of kids are overweight?

Asked by: John Martin
School: St. James Middle School
Grade: 8
Teacher: Mrs. Walter
Hobbies/Interests: Sports

Answer from Jennifer Wegmann

Lecturer, Binghamton University

Research area Eating disorders and body image Interests/hobbies: Exercising, reading, writing Family: Husband, Tom; two Sons - Nick (11) & TJ (9)

Before I answer it is important to know how someone is diagnosed as overweight or obese. Currently in our country the Centers for Disease Control (CDC) diagnoses overweight and obesity by a measurement called a Body Mass Index (BMI). The measurement considers a person’s height and weight to estimate “fatness,” although it does not actually measure the amount of fat on a person’s body. In turn, this estimate is related to a person’s risk for disease, like heart disease, cancer, diabetes (type 2), high blood pressure and more. When calculating BMI’s for children and teens the measurements are also age and gender specific, often referred to as BMI for age. After a child or teen’s BMI is calculated it is then plotted in a growth chart, which is gender specific, and a percentile ranking is given. The growth charts then categorizes weight status (underweight, healthy weight, at risk of overweight, and overweight). For example a child ranked lower than the 5th percentile may be considered underweight. Where as a child ranked above the 95th percentile may be considered overweight. BMI calculators for children and teens can be found at www.cdc.gov.

The BMI is widely used because it is free, simple and measurements are consistent across all populations. All you need is a person’s height and weight. Having said that it is important to understand that there are limitations to BMI’s and there are individuals that will not get an accurate assessment from a BMI because the measurement does not differentiate fat from lean mass (like muscle). For example, we could compare two people who are the same age, height, & weight. One person may have a large amount of muscle mass and the other may have a larger amount of fat mass. When BMI’s are calculated for these two individuals the person with higher muscle mass could have a higher, less healthy, BMI reading (muscle weighs more than fat). The individual with the higher amount of fat could have a lower, healthier, BMI. In this example the healthier individual, the person with larger amounts of muscle mass, could actually be considered overweight or obese, while the individual with larger amounts of fat mass would find themselves in the acceptable category when in fact they are over fat (yet at a “healthy” weight). This is why for children and teens the BMI is not used as a diagnostic tool but rather a screening tool. If a child has a high BMI then a health care provider would need to do additional assessments to decide if there are looming health issues. Regardless of the limitations associated with BMI’s they are the standard measuring tool used in the United States.

Now to answer your question specifically, the CDC reports that 13.9% of children aged 2- 5 years, 18.8% of children aged 6-11 & 17.4 % of adolescents aged 12-19 are classified as overweight. Sadly, since 1976 each age group has seen a significant increase in the number of children being classified as overweight. Along with unhealthy weight gain, children and adolescents may develop health problems once seen, for the most part, in adults like type 2 diabetes, high blood pressure and cardiovascular disease. It is vital that we all take action to help curb childhood overweight and obesity trends. We all need to place emphasis on being active and eating a well balanced, moderate diet.

Last Updated: 9/18/13