SeriesSmart food policies for obesity prevention
Introduction
What works to prevent obesity? This question is often asked by policy makers and politicians, and in this Series paper, we address it in the realm of food policy. To do so, we explore how food-policy actions work. Our objective is to identify how such policies can be designed to be more effective. For the purposes of this paper, food policies are defined as actions that aim to improve the human diet. We focus on policies at the consumer-end of the food system, recognising that they have the potential to influence both supply and demand. We define effective food policies as those that successfully influence one of the key determinants of obesity: diet.
We start by reviewing the relevant evidence from psychology, economics, and public health nutrition to develop a theory of change through which food-policy actions could be expected to affect diet. We find that the interactions between people's environments and their food preferences are key in the identification of the mechanisms through which food policies work. We explore how actions in three specific policy areas (school settings, economic instruments, and nutrition labelling) work through these mechanisms. We use the theory of change and the evidence reviewed to provide guidance for the design, prioritisation, and assessment of effective food policies.
Section snippets
The theory of change
Theories of change are a useful method to understand complex problems such as obesity because they highlight the mechanisms through which interventions are expected to lead to specific changes, and how these changes might interact.1, 2 In this paper, we develop a theory of change to identify the key mechanisms through which food-policy actions work (figure). Four pieces of evidence were especially important in the formulation of the theory: first, the importance of food preferences in the
Testing of the theory: how have policy actions worked?
Can the mechanisms that drive this theory of change further an understanding of how food policies have worked? Here we review the evidence in three specific policy areas (school settings, economic instruments, and nutrition labelling), with the aim of identifying which—if any—of the mechanisms are at work. The review includes evidence from systematic reviews and assessments of implemented policy actions. We use the analysis to provide insights for improved policy design (table).
Principles and challenges
The analysis presented in this Series paper shows that the learning, expression, and reassessment of food preferences in the context of people's environments are important elements in understanding how food policies work. The evidence indicates that effective policy actions are those which change some aspect of the food, social and information environment around people and the systems that underpin them, are tailored to the preference, behavioural, socioeconomic, and demographic characteristics
How to design policy assessments
The analysis in this paper presents some important challenges for the measurement and interpretation of the effects of food-policy actions on diets and obesity. First, policy actions will take time to work when unhealthy preferences have already been learned. Second, actions are likely to affect different people in different ways. Third, the failure of an action could be due to poor design, such as the absence of mutually reinforcing actions. Fourth, the feedback effects of the policy on the
Moving forward
The analysis in this paper provides a more nuanced and sophisticated understanding of the role of food policy in addressing obesity. In essence, we have taken a systems approach2, 35, 55, 137, 148, 149, 150, 151 to addressing obesity by identifying some of the multiple distinct mechanisms at work in the complex system of interdependent interactions between people and their environments. The analysis has enabled us to understand how food policies can be designed more effectively to improve
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