Elsevier

The Lancet

Volume 385, Issue 9985, 13–19 June 2015, Pages 2410-2421
The Lancet

Series
Smart food policies for obesity prevention

https://doi.org/10.1016/S0140-6736(14)61745-1Get rights and content

Summary

Prevention of obesity requires policies that work. In this Series paper, we propose a new way to understand how food policies could be made to work more effectively for obesity prevention. Our approach draws on evidence from a range of disciplines (psychology, economics, and public health nutrition) to develop a theory of change to understand how food policies work. We focus on one of the key determinants of obesity: diet. The evidence we review suggests that the interaction between human food preferences and the environment in which those preferences are learned, expressed, and reassessed has a central role. We identify four mechanisms through which food policies can affect diet: providing an enabling environment for learning of healthy preferences, overcoming barriers to the expression of healthy preferences, encouraging people to reassess existing unhealthy preferences at the point-of-purchase, and stimulating a food-systems response. We explore how actions in three specific policy areas (school settings, economic instruments, and nutrition labelling) work through these mechanisms, and draw implications for more effective policy design. We find that effective food-policy actions are those that lead to positive changes to food, social, and information environments and the systems that underpin them. Effective food-policy actions are tailored to the preference, behavioural, socioeconomic, and demographic characteristics of the people they seek to support, are designed to work through the mechanisms through which they have greatest effect, and are implemented as part of a combination of mutually reinforcing actions. Moving forward, priorities should include comprehensive policy actions that create an enabling environment for infants and children to learn healthy food preferences and targeted actions that enable disadvantaged populations to overcome barriers to meeting healthy preferences. Policy assessments should be carefully designed on the basis of a theory of change, using indicators of progress along the various pathways towards the long-term goal of reducing obesity rates.

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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