FIGURE 3-1 Simplified ecological systems theory model.

intake exceeds energy expenditure (Figure 3-2). Both aspects of energy imbalance (i.e., food and beverage intake and physical activity) interact with and are affected by multiple factors within each of the four ecological layers. The two innermost layers describe factors operating within the individual (including genetic factors, ethnic identity and culturally determined attitudes and beliefs, psychosocial factors, and current health status) and those operating within the physical and social locations and situations that define daily behavioral settings (Booth et al., 2001). The key behavioral settings for children and youth are the home, school, and community. As noted in the framework developed by the Partnership to Promote Healthy Eating and Active Living, behavioral settings are affected either directly or indirectly by a variety of other factors that potentially constitute primary and secondary leverage points for effecting changes (Booth et al., 2001). These leverage points include the major sectors that affect the food system, opportunities for physical activity or sedentary behavior, and information and education regarding dietary behaviors and physical activity. The outermost layer on the framework in Figure 3-2 reflects the critical concept of an overlay of social norms and values, that is, the social fabric that cuts across all the layers and processes below. Social norms and values both determine and respond to collective social and institutional processes within the con-



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