Reflections on expert consensus: a case study of the social trends contributing to obesity

Background: In Australia, as elsewhere in the developed world, researchers and policy makers have expressed concern about rising rates of obesity. Explanations for the increasing weight of the Australian population have focused on both declining levels of physical activity and changes in food consumption patterns. Methods: The primary aim of our study was to determine the views of obesity, dietary and physical activity experts, about the most important social trends that have contributed to Australia's obesogenic environment over the last 50 years. We used a modified Delphi technique to successfully contact 50 such experts to obtain their views on this topic. The process involved a semi-structured interview with each expert to identify the trends and then a round of ranking of the trends by these experts. A second aim was to comment on the utility of expert opinion in public policy. Results: The experts identified the most important social trends as ‘escalating car reliance’, ‘increasing “busy-ness” and lack of time’ and ‘rising use of convenience and pre-prepared food’. Because we asked experts to explain their responses, a diversity of opinion emerged on both the aetiology of these trends and how the environment is embodied to produce rising levels of obesity. Conclusion: We reflect on the implications of this dissensus for the utility of expert opinion in public policy and argue that one way through the smorgasboard of competing expert explanations for health differentials, including obesity levels, is practice-based evidence gathered through community level action research.