Stemming the global obesity epidemic: what can we learn from data about social and economic trends?

Although the policy debate is only slowly moving away from the focus on individual-level psychological and social factors, the research community has largely recognized that changes in dietary and physical activity patterns are driven by changes in the environment and by the incentives that people face. Many factors have been suggested as causes of the 'obesity epidemic'. Putting a multitude of isolated data points into a coherent picture is a challenging, but necessary, task to assess whether proposed solutions are promising or likely to lead down a blind alley. Conventional wisdom is an unreliable guide and some widely held beliefs are incorrect. Can one distinguish between important and less important behavioural changes and relate them to environmental incentives? People face trade-offs in allocating their scarce resources of time and money to best achieve their goals, including health. Studying what people are doing with their time and money is a good start towards understanding how economic incentives have altered energy intake and energy expenditure in a way that has led to weight gain. A challenging task for policy will be finding the right levers. Both economic and public health/medical perspectives play an important role in the policy process, but often approach policy questions in an incompatible way. Economics and public health perspectives can complement each other, but harnessing any synergy requires an understanding of the other perspective. Arguably the most effective community intervention would be multi-faceted and would include several goals about diet and physical activity. In practice, however, it appears that much more effort is devoted to promoting increased fruit/vegetable consumption, and exhorting individuals to increase physical activity than to environmental intervention that would make it easier for people to reduce energy intake and sedentary entertainment. Politically, it may often be more expedient to promote an increase than a decrease, but it may be far less effective.