Spring/Summer 1997

Increased Prevalence of Overweight in Preschoolers
Shows Need for Early Intervention

In the last 20 years, the prevalence of overweight increased among 4- and 5-year olds but not among younger children. These findings suggest efforts to prevent overweight, such as encouraging physical activity and a healthy diet, should begin in early childhood, according to Cynthia L. Ogden,Ph.D., of the Centers for Disease Control and Prevention's National Center for Health Statistics (NCHS) and the lead author of "Prevalence of Overweight among Preschool Children in the United States, 1971-1994,"published in the April 1, 1997, Pediatrics electronic pages.

The authors examined the prevalence of overweight in U.S. preschool children, ages 2 months through 5 years, using data from the first National Health and Nutrition Examination Survey (NHANES I), 1971 through 1974; NHANES II, 1976 through 1980; Hispanic Health and Nutrition Examination Survey, 1982 through 1984; and NHANES III, 1988 through 1994. Between 1,200 and 7,500 children younger than 6 years of age were examined in each of the four surveys.

The prevalence of overweight was defined as the percentage of children, ages 2 through 5, whose weight-for-stature or weight-for-length fell above the 95th percentile of the respective growth curve on the NCHS growth chart for children*. Researchers recommend this cut-off point in the body mass index (BMI) because of possible changes in weight status as children grow and develop. BMI is equal to weight in kilograms divided by height in meters squared.

Based on NHANES data, more than 10 percent of children, 4 to 5 years of age, were overweight in 1988 through 1994, compared with 5.8 percent in 1971 through 1974. During these time spans, no change was evident in overweight prevalence among children, 1 to 3 years of age. During 1988 through 1994, the prevalence of overweight among children, 2 months to 5 years old, was consistently higher in girls than in boys.

From NHANES I to NHANES III, researchers found no change in the prevalenceof overweight among children, 2 to 3 years of age, but there was an increase among children, 4 to 5 years of age, especially in girls.

The prevalence of overweight among girls was higher than among boys for all racial/ethnic and age groups. Currently, 10.8 percent of girls, 4 to 5 years of age, are overweight.

According to the authors, the higher prevalence of overweight among girls may be attributable to gender differences in behavior. In at least one study, preschool boys were found to be more physically active than preschool girls, and similar gender differences in overweight prevalence have been observed in older children and adults.

The reasons for the increase in overweight prevalence among children, 4 to 5 years of age, are complex. Excess weight gain is ultimately a result of energy intake exceeding energy expenditure, with sociocultural factors influencing lifestyle and diet choices.

The influence of bottle feeding, early introduction of solid foods, balanced food selection, and other dietary practices on overweight in preschool-aged children is less clear. NHANES dietary intake data suggest that mean energy and fat intake among preschoolers have not increased in the last 20 years.

The increasing prevalence of overweight among children, 4 to 5 years of age, indicates that prevention activities need to begin in the preschool years. As recommended in Nutrition and Your Health: Dietary Guidelines for Americans, these efforts include encouraging physical activity to maintain a healthy weight, eating at least five servings of fruits and vegetables daily, and after age 2, gradually decreasing dietary fat to a level of no more than 30 percent of calories a day.

Overweight among preschool children is a concern because it may have long-term health consequences. Excess body weight in childhood is associated with overweight in adulthood, and excess body fat or obesity is recognized as a health risk. Obesity and overweight in childhood have also been linked to subsequent morbidity and mortality in adulthood, and overweight preschoolers have been shown to have higher mean levels of cholesterol than other children. "Pediatric practitioners should emphasize the importance of diet and physical activity as two components of a healthy lifestyle, with more emphasis on adequate amounts of physical activity," says Dr. Ogden.

"Clinical, community, and national examination of weight among preschool children must continue. We need to investigate the factors associated with overweight among preschoolers. Researchers also must assess what the dietary habits and activity levels are for different sociocultural groups," she says.

Study coauthors with Dr. Ogden are: Richard P. Troiano, Ph.D., R.D.; Ronette R. Briefel, Dr.P.H., R.D.; Robert J. Kuczmarski, Dr.P.H., R.D.; Katherine M. Flegal, Ph.D.; and Clifford L. Johnson, M.S.P.H. The study findings are available on the World Wide Web at http://www.pediatrics.org/cgi/content/full/99/4/el.

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* Hamill, P.V.V., et al., "Physical growth: NCHS percentiles," Am. J. Clin. Nutr., 32: 607-629, 1979.