ADOLESCENT OBESITY: PREVALENCE AND IMPORTANCE
The prevalence of obesity in childhood and adolescence has increased dramatically in the United States and in all developed countries since the early 1970s. Throughout childhood, obesity is defined as a body mass index (BMI) at or above the 95th percentile for age and sex using standard Centers for Disease Control and Prevention (CDC) growth curves; overweight is defined as BMI greater than the 85th to the 94th percentile. From National Health and Nutrition Examination Surveys (NHANES) data, the prevalence of obesity in 12- to 19-year-olds was 6.1% in 1971–1974 and increased serially at each evaluation to 20.5% in 2011–2012 (Figure 4-1).1 Overall, 23.9 million American children (32% of boys and 31.6% of girls) have a BMI at or above the 85th percentile and are classified as overweight or obese.2
Trends in obesity among children and adolescents aged 2–19 years, by sex: United States, selected years 1971–1974 throughout 2011–2012. (From Fryar CD, Carroll MD, Ogden CL. Prevalence of Overweight and Obesity Among Children and Adolescents: United States, 1963–1965 Through 2011–2012. Atlanta, GA: National Center for Health Statistics; September 2014. Retrieved December 19, 2014. www.cdc.gov/nchs/data/hestat/obesity_child_11_12/obesity_child_11_12.pdf).
There are major discrepancies in obesity prevalence by sex, by racial and ethnic group, and by socioeconomic status (SES). From NHANES 2011–2012, 18.3% of non-Hispanic white male adolescents and 20.9% of non-Hispanic white female adolescents were obese compared with 21.4% of non-Hispanic black males and 22.7% of non-Hispanic black females, 23.9% of Hispanic males and 21.3% of Hispanic females, and 14.8% of Asian males and 7.3% of Asian females.1 Using parental education as an SES standard, data from NHANES and from the National Survey of Children’s Health show that, since 2002, obesity rates have declined to less than 10% in adolescents whose parents have at least a 4-year college degree, close to the prevalence in 1970; this compares with a prevalence of 20%–25% in adolescents whose parents have at most a high school education.3
The severity of obesity has also been increasing exponentially over time. Severe obesity is defined as BMI greater than 120% of the 95th percentile for age/sex or an absolute BMI greater than 35 kg/m2. From NHANES data, the prevalence of severe obesity is 5%–7% in males and 4%–6% in females.4 This is the fastest-growing subcategory of obesity in children and adolescents, in males and females, and in all racial/ethnic groups.5
Taken together, these statistics provide overwhelming evidence that obesity is an important problem for those who provide health care to adolescent females. In addition, obesity tracks strongly from childhood into adulthood, with an overall predicted prevalence of about 70%.4 In the Bogalusa Heart Study, of those with severe obesity at 12 years of age, 100% were obese as adults; 65% ...