In June 2007, the National Cancer Institute (NCI) convened a half-day meeting aimed at identifying research priorities and other issues related to environmental and policy influences on diet, physical activity, energy balance, and health behavior that could effect positive change in the obesity epidemic at the population and societal levels. This paper provides an overview of the meeting's background and structure, reports on the outcomes from the meeting, and concludes with a discussion of obesity policy research topic areas, key themes from the meeting discussions, and implications for obesity policy research.
The rise in obesity levels in the U.S. in the past several decades has been dramatic, with alarming implications for public health and the economy. By the metrics developed in the Healthy People 2010
the prevalence of obesity is unacceptably high in all social and economic groups, in both genders and in all age groups. Sustained, corrective shifts in energy intake and expenditure will be needed to reduce current obesity levels.
Obesity has serious health and economic implications. It is a known risk factor for a wide range of chronic diseases, debilitating conditions, and psychosocial problems.2–4
Widespread obesity has not only devastating human costs, but also growing direct and indirect costs that threaten to overwhelm public and private healthcare budgets and broadly affect the economy. Researchers have estimated that 9.1% of U.S. healthcare spending in 1998—$78.5 billion ($105.9 billion in 2008 dollars)—was the result of conditions related to overweight and obesity. Half of this sum was financed by Medicare and Medicaid.5
General healthcare spending in the U.S. has increased from 7.2% of gross domestic product (GDP) in 1970 to 16% in 2006,6
and it is projected to rise to 19.5% of GDP by 2017.7
A study by Thorpe and colleagues8
estimated that 27% of the rise in healthcare spending between 1987 and 2001 was explained by obesity. In addition to direct healthcare costs, obesity increases indirect costs, such as disability, absenteeism, and decreased productivity.9
The causes of the rise in obesity levels are simultaneously straightforward and complex. Weight gain is the result of energy intake exceeding expenditure over time, and energy balance has obviously been positive for many people. Evidence suggests that average caloric intake in the U.S. has increased in recent decades10,11
and that the per-capita energy available in the nation's food supply is higher now than during any period in the past century.12
In addition, it is clear that the total energy expenditure associated with physical activity has not compensated for this increase in intake. 13–16
The understanding of the contribution of genetics to obesity is increasing rapidly. However, genetics alone cannot explain the increase in overweight and obesity rates. Instead, it seems likely that the rise in obesity prevalence stems from a complex array of environmental factors that—in combination with genetics—affect diet, physical activity, sleep, and other human behaviors that are currently understood to influence weight change. Environmental correlates of increasing obesity prevalence span the community, societal, national, and international environments. These correlates include: increased portion sizes17,18
; school food and physical activity environments19–21
; the physical form of communities, or the built environment15,22,23
; the community food environment24–28
; relatively high costs of fresh produce and other nutrient-dense foods29
; technologic advances leading to decreased costs of food and reduced requirements for physical activity30,31
; and marketing of high-calorie and low-nutrient food, especially to children.20,32
The rapid rise in obesity rates and the evidence of environmental influences have stimulated interest in examining the potential for broad systemic changes, including policy initiatives, to modify the food and physical activity environments in ways that may foster the sustained changes needed to reduce obesity at the population level. Policy is recognized as a powerful instrument to influence public health generally,33,34
and public health policies aimed at reducing tobacco use (e.g., tobacco tax increases; smoke-free air laws; restrictions on product packaging, labeling, promotion, and youth access; changes to subsidies and agricultural policies; counter-advertising) have altered the environment in which individuals make choices about tobacco use and cessation. Policy-based strategies have been very effective as methods of tobacco control,35,36
and they have formed the basis of many other successful public health initiatives, including seat belt use, vaccinations, and occupational safety.34,37,38
A growing number and variety of policies are being implemented that are intended to promote healthy eating and physical activity patterns in order to achieve healthy body weight at local and state levels of government. Many of these have targeted the food environment and activity requirements in schools. Although there are promising findings from research interventions at school, community, and state levels, relatively little is known about the absolute and relative effects of policy changes on diet and physical activity behavior and health outcomes. Additional research is clearly needed to examine the potential impact of proposed policies and to evaluate and quantify the effects of newly implemented policies designed to address obesity. Findings from these and other studies may help to inform future policy decision-making and resource allocation.
In light of (1) the link between obesity and adverse health conditions, (2) the paucity of existing research, and (3) the powerful effects of policy interventions seen in tobacco control, NCI and other NIH groups are interested in identifying promising research directions that can contribute to the evidence base of how best to effect positive population-level change to reduce obesity and promote improved health among Americans. Strategies to foster such shifts will need to address environmental and policy influences on nutrition and physical activity behaviors in addition to influences that act at the individual level. Some initial research activities have begun at NCI to foster research that may be relevant to policy in this area (see, for instance, www.appliedresearch.cancer.gov/funding/econ_diet_act_ener_fact_sheet.pdf
). In addition, NIH, the CDC, and the Robert Wood Johnson Foundation (RWJF) are working together to identify areas for collaborative efforts on this topic. Leadership in research in this area is consistent with the component of the NIH mission that calls for applying knowledge to extend healthy life and reduce the burdens of illness and disability. The following sections discuss the process and outcomes of the meeting convened by NCI.