OPALesence: epistemological pluralism in the evaluation of a systems-wide childhood obesity prevention program

The evaluation of complex systems-wide public health interventions requires evaluation research that is underpinned by theory. This article presents and discusses the trans-disciplinary evaluation research framework developed to support the evaluation of a South Australian program called OPAL (Obesity Prevention and Lifestyle). The aim is to provide insights into the research design, methods and implementation of the evaluation and contribute to the debate on how to evaluate community-based interventions with complicated and complex aspects. In an attempt to capture the complexity of childhood obesity and the intervention, the OPAL evaluation research employs post positivist, interpretive and critical epistemologies, valuing epistemological pluralism. Each component of the multi-phase mixed methods evaluation captures different yet complementary information concerning the context, process, cost effectiveness and outcomes providing a more complete understanding of the impacts of the complex program. Evaluation research is not without challenges. Some of the tensions and challenges that arose in the establishment, planning and conduct of the OPAL program and evaluation are discussed.