National Institutes of Health Pathways to Prevention Workshop: Methods for Evaluating Natural Experiments in Obesity.

On 5 and 6 December 2017, the National Institutes of Health (NIH) convened the Pathways to Prevention Workshop: Methods for Evaluating Natural Experiments in Obesity to identify the status of methods for assessing natural experiments to reduce obesity, areas in which these methods could be improved, and research needs for advancing the field. This article considers findings from a systematic evidence review on methods for evaluating natural experiments in obesity, workshop presentations by experts and stakeholders, and public comment. Research gaps are identified, and recommendations related to 4 key issues are provided. Recommendations on population-based data sources and data integration include maximizing use and sharing of existing surveillance and research databases and ensuring significant effort to integrate and link databases. Recommendations on measurement include use of standardized and validated measures of obesity-related outcomes and exposures, systematic measurement of co-benefits and unintended consequences, and expanded use of validated technologies for measurement. Study design recommendations include improving guidance, documentation, and communication about methods used; increasing use of designs that minimize bias in natural experiments; and more carefully selecting control groups. Cross-cutting recommendations target activities that the NIH and other funders might undertake to improve the rigor of natural experiments in obesity, including training and collaboration on modeling and causal inference, promoting the importance of community engagement in the conduct of natural experiments, ensuring maintenance of relevant surveillance systems, and supporting extended follow-up assessments for exemplar natural experiments. To combat the significant public health threat posed by obesity, researchers should continue to take advantage of natural experiments. The recommendations in this report aim to strengthen evidence from such studies.