Although the prevalence of overweight and obesity among US children is a concern for many health care professionals, incidence rates over time seem to be variable, depending on the assessment measurements used. It is difficult to determine the associated health implications of pediatric obesity or overweight, especially the type that might result in adult obesity or overweight. This review examines the various factors that contribute to the weight and fitness status of children, including anthropometric factors, nutrient intake, the level of physical activity, and nutrition knowledge. Nutrient intake data of the past decade show that the energy and fat intakes of children in the United States have been fairly constant. However, data also indicate that their physical activity has declined. The data strongly suggest that the apparent prevalence of pediatric overweight may not be so much a function of nutrient intake as of a decrease in physical activity leading to an imbalance of energy input and output.