The Rising Epidemic of Childhood Obesity
Overweight and obesity in children are significant public health problems in the United States. The number of adolescents who are overweight has tripled since 1980 and the prevalence among younger children has more than doubled. According to the 1999-2002 National Health and Nutrition Examination Survey (NHANES), 16 percent of children age six to nineteen years are overweight. (1, 2, 3) Not only have the rates of overweight increased, but the heaviest children in a recent NHANES were markedly heavier than those in previous surveys.
Obesity disproportionately affects certain minority youth populations. NHANES found that African American and Mexican American adolescents ages twelve to nineteen were more likely to be overweight, at 21 percent and 23 percent respectively, than non-Hispanic White adolescents (14 percent). (4) In children six to eleven years old, 22 percent of Mexican American children were overweight, whereas 20 percent of African American children and 14 percent of non-Hispanic White children were overweight. (5) In addition to the children and teens who were overweight in 1999-2002, another 15 percent were at risk of becoming overweight. (6, 7) In a national survey of American Indian children five to eighteen years old, 39 percent were found to be overweight or at risk for overweight. (8)
Being overweight during childhood and adolescence increases the risk of developing high cholesterol, hypertension, respiratory ailments, orthopedic problems, depression and type 2 diabetes as a youth. One disease of particular concern is type 2 diabetes, which is linked to overweight and obesity and has increased dramatically in children and adolescents, particularly in American Indian, African American and Hispanic/Latino populations. (9) The hospital costs alone associated with childhood obesity were estimated at $127 million during 1997-1999 (in 2001 constant U.S. dollars), up from $35 million during 1979-1981. (10)
Looking at the long-term consequences, overweight adolescents have a 70 percent chance of becoming overweight or obese adults, which increases to 80 percent if one or more parent is overweight or obese. (11) Obesity in adulthood increases the risk of diabetes, high blood pressure, high cholesterol, asthma, arthritis, and a general poor health status. (12) In 2000, the total cost of obesity for children and adults in the United States was estimated to be $117 billion ($61 billion in direct medical costs). (13)
Understanding the causes of childhood obesity can provide the opportunity to focus resources, interventions and research in directions that would be most beneficial in addressing the problem. The remainder of this document provides an overview of the existing research into the causes of childhood obesity, and a discussion of data limitations.
The causes of childhood obesity are multi-factorial. Overweight in children and adolescents is generally caused by a lack of physical activity, unhealthy eating patterns resulting in excess energy intake, or a combination of the two. Genetics and social factors--socio-economic status, race/ethnicity, media and marketing, and the physical environment--also influence energy consumption and expenditure. Most factors of overweight and obesity do not work in isolation and solely targeting one factor may not make a significant impact on the growing problem.
To date, research has been unable to isolate the effects of a single factor due to the co-linearity of the variables as well as research constraints. (14) Specific causes for the increase in prevalence of childhood obesity are not clear and establishing causality is difficult since longitudinal research in this area is limited. Such research must employ long study times to discern if there is an interaction of factors leading to an increase in the prevalence or the prevention of obesity during childhood and adolescence. Underreporting total food intake, misreporting of what was eaten, and over reporting physical activity are all likely potential biases that may affect the outcomes of studies in this area. …