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Study Designs and Analytic Strategies for Environmental and Policy Research on Obesity, Physical Activity, and Diet: Recommendations from a Meeting of Experts

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Abstract

Numerous authoritative reports have identified environmental and policy interventions as the most promising strategies for creating population-wide improvements in diet, physical activity, and obesity. Yet many methodologic challenges to conducting environmental and policy research must be overcome to enable this area of study to advance. A meeting titled “Study Designs and Analytic Strategies for Environmental and Policy Research on Obesity, Physical Activity, and Diet” was held April 8, 2008. Participants from diverse backgrounds identified priority gaps in knowledge and generated recommendations for promising methods to enhance environmental and policy research related to obesity. Final recommendations were based on a postmeeting participant survey.

Existing methods were identified that could be applied to advance the field, including prospective studies, evaluations of natural experiments, and economic studies. Training for investigators in the use of appropriate statistical methods for complex designs and interdisciplinary collaboration were recommended. Methodologic research priorities included the development of measures of policy, health impact assessments, and the investigation of policy adoption and implementation. The results of this conference can be used to improve the quality and quantity of environmental and policy research as well as the translation to action to control obesity.

Introduction

Obesity is one of the most serious and prevalent health problems in the U.S. Two thirds of adults and one third of children and adolescents are either overweight or obese, with low-income and certain racial/ethnic populations disproportionately affected.1, 2 Although multiple genetic loci create predispositions to obesity, it is widely believed that alterations of environments have caused changes in dietary and physical activity behaviors, triggering the current epidemic.3, 4 Numerous health authorities have identified environmental and policy interventions as the most promising strategies for creating population-wide improvements in eating, physical activity, and obesity, including reports by the U.S. Surgeon General,4 WHO,5 the IOM,6, 7 the CDC,8 and the International Obesity Task Force.9

Evidence is growing rapidly that the attributes of built environments, including neighborhood design and lack of access to attractive parks, are associated with obesity10 and physical activity.11, 12 Food-environment attributes such as the lack of access to supermarkets and the concentration of fast-food restaurants also are related to excess energy intake and obesity.13, 14, 15, 16 However, there are special challenges to conducting environmental and policy research that could undermine the momentum in this area of study, compromise advancements in understanding obesity-related environmental and policy etiologic factors and interventions, and delay the development of evidence-based solutions to the obesity epidemic. Three methodologic concerns can be identified.

  • 1

    There are limited RCTs that intervene on environmental or policy factors. Investigators rarely are able to control environmental or policy factors, so RCTs are impossible in most situations. For example, zoning codes, grocery store–location decisions, and park renovations are outside the control of investigators. Thus, the vast majority of studies to date are cross-sectional, which limits the advancement of the science and its credibility for guiding policy change.

  • 2

    There are analytic challenges because most environmental and policy studies have nested or other complex data structures that presumably require multilevel or spatial statistics. Additionally, there is confounding between the characteristics of residents of neighborhoods and the characteristics of those environments, presenting a difficult selection problem in observational studies. There is a need to develop innovative statistical models tailored to the demands of environmental and policy studies.

  • 3

    Although the development of built environment and food environment measures is proceeding, the development of measures of policies has lagged. Few investigators in this field are familiar with the measurement of policy variables, so methods and perspectives need to be adapted from other fields. Advancing the field will require interdisciplinary teams of researchers and the building of a diverse network of researchers. Policy measurement could entail research that investigates the factors supporting the successful adoption and implementation of a particular policy. Policy measurement could also involve understanding a policy's impact on changing the built and the food environments.

As an initial step in improving the methodology of environmental and policy research related to obesity, diet, and physical activity, a national meeting of experts was organized to develop and prioritize recommendations. The conference was responsive to the first theme of the strategic plan for NIH Obesity Research (obesityresearch.nih.gov): “Research toward preventing and treating obesity through lifestyle modification.” The conference contributed to improving methodology for studies consistent with the NIH Obesity Research goals:

Under this theme, the goals and strategies for achieving them encompass identifying modifiable behavioral and environmental factors that contribute to the development of obesity in children and adults, and designing and testing potential intervention strategies.

The conference targeted methodologies central to both etiologic and intervention research on environmental and policy issues. For purposes of this conference, the dietary behaviors most related to obesity were of interest, and physical activity could include the entire spectrum of types and intensities as well as sedentary behaviors.

The conference identified high-priority gaps in knowledge and considered the relevance of recommendations for contributing to understanding and eliminating disparities in obesity, diet, and physical activity. A high priority was placed on involving new and minority investigators in this conference, including those with personal experience in and insights about the low-income populations and communities of color disproportionately affected by obesity, to expand both this new and evolving field and these investigators' capacity to conduct important research.

The conference objectives were to:

  • identify the highest-priority gaps in knowledge on environment and policy factors that influence obesity, diet, and physical activity;

  • identify promising study designs to enhance the quality and rigor of environmental and policy research on obesity, diet, and physical activity;

  • identify promising analytic strategies that can be applied to improve environmental and policy research on obesity, diet, and physical activity;

  • identify measures of policies of particular relevance to obesity prevention that either can be used in research or need to be developed;

  • identify other strategies that can advance the research field, such as commissioned papers, think-tank meetings, curriculum design, and training; and

  • build the capacity of new investigators to make important contributions to environmental and policy research on obesity, diet, and physical activity.

Section snippets

Methods

The organizing committee (Table 1) developed the conference goals, format, methods, and participant invitation list. NIH staff served on the organizing committee and played important roles in planning the conference and facilitating the dissemination and use of the recommendations.

The full report of the conference, including slide presentations, is available on websites (www.activelivingresearch.org and www.healthyeatingresearch.org), and the highlights are summarized here. The 1-day

Conclusion

The continuing obesity epidemic is one of the most serious threats to health in the U.S. and across the globe.1, 2, 3, 4, 5 Although public health authorities have identified environmental and policy changes as essential to controlling the obesity epidemic,3, 4, 5, 6, 7, 8, 9 research to generate evidence-based solutions is hampered by methodologic challenges. The conference described here engaged a diverse group of investigators and funders to recommend strategies for advancing environmental

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