multifrequency bioelectrical impedance analysis data on participants aged 8 to 49 years and dual energy x-ray absorptiometry measures on participants older than 8 years of age. This information allows greater accuracy in determining body-weight status and in examining correlates of nutrition and physical activity. NHANES data are used to track trends in obesity prevalence. But it is critical that additional information be collected and analyzed to provide insights into obesity prevention efforts.

Many of the current surveillance efforts collect data on only one age range (most often adolescents) and usually lack the resources to focus on high-risk populations at the state and regional levels. More detailed information is needed on weight status; physical activity; nutrition; social, environmental, and behavioral risk factors for obesity; and economic and medical consequences of obesity (such as type 2 diabetes in children and youth). Information on children’s physical activity levels is particularly scant because most national surveys focus on adolescents. Additional information is needed at the state and regional level to provide more in-depth information on specific geographic areas or high-risk populations. Further efforts should also be made to monitor community-level variables in order to assess the impact of environmental-level changes and policies. Examples include the number of school districts requiring daily physical education in schools, the number of grocery stores selling fresh fruits and vegetables within low-income neighborhoods, or the percentage of children living within a mile of school who commute by walking or biking. Innovative approaches should be explored and evaluated that would monitor the impact of changes at the local level and feed that information back to national sources so that successful programs could be refined and expanded.

Relevant surveillance and monitoring efforts should be supported and strengthened by increased federal funding; this applies particularly to NHANES, as it is a valuable information resource for obesity prevention programs. Special efforts should be made to identify those populations most at risk of childhood obesity, and to monitor the social, environmental, and behavioral factors contributing to that elevated risk.

Further efforts to collect longitudinal data would be useful, as longitudinal studies can examine potential risk factors associated with the development of obesity and normal weight, which is not possible from cross-sectional studies. Discussions are ongoing about initiating a new national longitudinal study on U.S. children that would follow a large cohort over time to examine health and well-being issues. As this national study is being considered, the committee urges that weight status, as well as nutrition- and physical activity-related measures, be included in such an effort’s basic set of questions. A precedent is the Avon Longitudinal Study of Pregnancy and Childhood (ALSPAC), based in England and involving other European collaboration centers. ALSPAC is examining nutrition and other anteced-



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