Childhood Overweight: What the Research Tells Us

 (Revised March 2005)

• Overview
• Health Consequences of Childhood Overweight 
• Nutrition and Schools 
• Physical Activity and Schools 
• Schools Can Help 
• References 

Overview

The rapid increase in overweight among children and adolescents is generating widespread concern. Since the 1970s, the prevalence of overweight among children has more than doubled for preschoolers ages 2-5 and adolescents ages 12-19, and it has more than tripled for children 6-11 years.¹ Nearly one-third of children and adolescents, of both sexes, aged 6-19 years (31.0%) are considered to be either at risk for overweight or overweight, defined as at or above the 85th percentile of the sex-specific BMI-for-age growth chart, and 16% are overweight or at or above the 95th percentile of the sex-specific BMI-for-age growth chart.²

On average, rates of overweight for boys and girls remain similar. Although the percent-age of overweight children and adolescents increased from the 1960s to 2002, the rates remain similar for boys and girls. For the years 1999-2002, among boys ages 6-19, 29.2% are at risk for overweight or were overweight. Among girls ages 6-19 during the same time period, 27.0% were at risk for overweight or were overweight.² 

 

Some groups of children are more affected by overweight than others. Among boys and young men, risk of overweight and overweight is a particular burden among those of Mexican American descent, with 42.8% of Mexican Americans ages 6-19 either at risk of over-weight or overweight compared with 31.0% of non-Hispanic black boys and adoles-cents and 29.2% of non-Hispanic white boys and adolescents. Among girls and young women, 40.1% of non-Hispanic black young people are at risk of overweight or over-weight, compared to 36.6% of Mexican American girls and young women and 27.0% of non-Hispanic white girls and young women.²

Definitions

The CDC uses the following definitions for measuring childhood overweight:⁴

• At risk of overweight: BMI-for-age > 85th percentile to < 95th percentile
  
• Overweight: BMI-for-age > 95th percentile

Body mass index (BMI) is the ratio of weight-to height, a formula in which a person’s body weight in kilograms is divided by the square of his or her height in meters–wt/(ht).^{2, 5} For children ages 2–20 years, BMI is plotted on a growth chart specific for age and gender. ⁶

Overweight in children and adolescents cannot be measured or discussed in the same terms used with adults. Because of uncertainty about the meaning of weight tables for growing children and a concern about the stigmatizing potential of the term “obesity,” some researchers use the CDC terminology. Other researchers use the term “childhood obesity.” Regardless of definition, the increase in the number and percent of children who are overweight is not disputed nor is the concern for its health consequences.

Researchers commonly use definitions developed for adult obesity by an NIH Expert Panel: overweight is a BMI of 25-29.9 kg/m², and obesity is a
BMI of 30 kg/m² or greater. Severe obesity is defined as having a BMI > 40, or > 35 with comorbid conditions.⁷ However, overweight and obesity are not mutually exclusive, since people who are obese are also overweight.⁸

 

Next: Health Consequences of Childhood Overweight