critical justification is that an obese adult population is an incubator, biologically and environmentally, for childhood obesity.

This chapter describes the charge and scope of the IOM Committee on an Evidence Framework for Obesity Prevention Decision Making, as well as the approach the committee took to fulfill its task. It also sets forth the case for viewing obesity as a problem of whole populations and for conceptualizing prevention strategies from a population perspective. Finally, it provides an orientation to the broad array of decisions of potential interest with respect to obesity prevention.

STUDY CHARGE, APPROACH, AND SCOPE

Several prior IOM committees have faced the need to work around evidence gaps and the fact that evidence hierarchies applied to medical treatment have limitations for assessing population-based preventive interventions. A committee tasked to develop a national action plan for child obesity prevention ultimately developed a set of principles to guide its process for reviewing evidence and making recommendations. These principles underscored the need for evidence to “inform and guide policy and programmatic decisions.” That committee also emphasized that the “absence of experimental evidence does not indicate a lack of causation or the ineffectiveness of an obesity prevention intervention,” that circumstances warrant taking preventive actions “even if there is as-yet-incomplete scientific evidence on the interventions,” but also that “there is an obligation to accumulate appropriate evidence not only to justify a course of action but to assess whether it has made a difference” (IOM, 2005, pp. 111, 114). The committee defined evidence broadly to include several types of quantitative and qualitative research studies or data that it consulted as appropriate to the type of question being answered and used an integrated approach that included multiple types of evidence, drawing on an approach then under development by an international organization. One of the hallmarks of the committee’s report was the use of historical case analyses—a social science method—applied to other complex public health scenarios as an alternative to typical traditional biomedical research studies.

The specific need for evidence on the effectiveness of interventions undertaken in various sectors and contexts was addressed by the IOM Committee to Assess Progress in Preventing Childhood Obesity (IOM, 2007). The IOM Committee on Food Marketing to Children and Youth (IOM, 2006) also highlighted several evidence issues and gaps that influenced its systematic review of evidence linking food and beverage marketing to childhood obesity or its behavioral determinants. Most recently, the IOM Committee on Local Government Actions to Prevent Childhood Obesity (IOM, 2009) followed the previous IOM recommendation to use the “best available evidence” rather than wait for the “best possible evidence” (IOM, 2005, p. 3) to recommend obesity prevention approaches based on potential effectiveness, impact, and suitability for local settings and authority. In light of the limitations of the current evidence base, that committee chose not to rank the recommended approaches. This deci-



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