ronmental outcomes in society or the community—which impact cognitive, social, and behavioral outcomes in individuals. A range of potential strategies and actions can be applied to achieve the intermediate outcomes.

At the left of the model, the potential for these strategies and actions to be undertaken by various sectors (government, industry, communities, schools, and homes) is indicated. The specifics of resources and inputs, strategies and actions, and outcomes that are relevant vary by sector. How this logic plays out sector by sector is included in the prior committee’s report (IOM, 2007). The demographic, sociocultural, and economic variables shown across the bottom of the figure as “cross-cutting factors” might define considerations for when targeted prevention is needed. The individual cross-cutting factors will determine the heterogeneity of effects on individuals and, therefore, the average effects on populations.

The logic model in Figure 2-2 illustrates some key points that will be revisited throughout the remaining chapters of this report. One is that the ultimate objective of obesity prevention activities is a change in BMI levels. Another is that change in BMI outcomes is achieved through activities that have an impact on four types of intermediate outcomes. The model emphasizes that many strategies undertaken to prevent obesity will not be expected to have an impact directly on BMI, but rather on pathways that will alter the context in which eating, physical activity, and weight control occur. This point has clear implications for the evaluation of evidence from obesity prevention studies with respect to how well the outcomes assessed match the actions in question. This report does not aim to give specific guidance as to which outcomes to assess; rather, it encourages users of the framework to think broadly when choosing outcomes, considering intermediate outcomes that lead to the ultimate objective of achieving and/or maintaining appropriate BMI levels.

Expert panels concerned both with dietary guidance generally and with the prevention of specific diseases emphasize the importance of obesity prevention (CDC, 2009; HHS, 2008; USDA/HHS, 2005; WHO, 2003, 2004; World Cancer Research Fund and American Institute for Cancer Research, 2007). For example, the 2005 Dietary Guidelines for Americans include a recommendation to “maintain body weight in a healthy range” and to “prevent gradual weight gain over time” (USDA/HHS, 2005, p. 14). The World Cancer Research Fund 2007 report (p. 373) includes a recommendation to “be as lean as possible within the normal range [defined as the appropriate ranges issued by national governments or WHO] of body weight.” These groups specify targets for obesity prevention based on population behaviors that may predispose to excess caloric intake or inadequate physical activity. These targets, supported by evidence with varying degrees of certainty, are summarized in Box 2-1. With a few exceptions, these targets apply to people of all ages and are therefore appropriate for both universal and targeted prevention strategies.

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