The World Health Organization (WHO) has recommended the use of fiscal policy to influence food prices "in ways that encourage healthy eating". (1,2) Although this is consistent with growing worldwide interest in the effect of fiscal policy on diet, (3-5) evidence supporting the use of taxes is weak. This review considers international evidence on the impact of food taxes and subsidies.
The current obesity epidemic reflects an increasingly "obesogenic" food environment and long-term changes in activity levels and energy expenditure. (6) Currently, financial incentives favour the consumption of highly processed, energy-dense foods since it is consistently cheaper, in terms of energy content for a given price, than less energy-dense and often more nutrient-rich foods. (7,8) Taxing less healthy foods could create a financial incentive for consumers to avoid them. Studies on the effect of manipulating food prices show that both individual consumers (9,10) and population groups (11-14) do respond as predicted.
The poor health outcomes associated with the consumption of energy-dense food (8,15) may justify levying taxes on such food to pay for health care and to decrease consumption, a measure that has proved effective for tobacco control. (16) However, taxation structures that worked for tobacco (i.e. an excise tax on a single provenly harmful substance) may not be readily transferable to food, which is essential for life and involves far more complex choices.
Very little evidence about the use of food taxes as a public health strategy is available. Cash & Lacanilao (17) examined pricing and taxation studies on food and concluded that more evidence is needed on the efficacy of taxation as a health intervention to support taking action. In a more recent review, Powell and Chaloupka (18) predicted that a small change in food prices would have little effect on body weight in the United States of America (USA), whereas a "non-trivial" change in food prices would affect body weight. They suggested that a combination of taxes and subsidies would have the greatest effect on body weight.
This review extends previous work on the effects of fiscal policy on food consumption patterns, obesity and chronic disease by updating evidence from the peer-reviewed literature and by incorporating carefully selected evidence from the non-peer-reviewed or grey literature, including modelling studies, all of which act as sources of evidence for policy-makers.
The Medline, ProQuest and Business Source Premier academic databases and Google Scholar were searched using the term "tax" or "subsidy" with the terms "food", "soft drink", "obesity" "diet", "nutrition", "consumption" and "fat", or their equivalent Medical Subject Heading terms, as appropriate. The first 150 articles identified from each search using Google Scholar were examined. Only English-language literature was included.
The criteria for including a study in this systematic review were that it: (i) was either an empirical or modelling study, (ii) examined a tax or subsidy on a specific food product (i.e. general agricultural subsidies or food taxes were excluded), and (iii) assessed the effect of the tax on a health outcome such as food consumption, body weight or disease. Empirical studies were defined as those that assessed the effect of an actual tax, while modelling studies were those that predicted rather than measured outcomes.
Articles were initially selected on the basis of their titles. Those whose abstracts were deemed irrelevant were then excluded, leaving 24 articles from Medline, 13 from ProQuest and 2 from Business Source Premier. In addition, 55 papers from Google Scholar were judged relevant. Once duplicate references were removed, 62 remained. Thereafter, 41 papers were excluded following a full text review, leaving 21. The reference lists from three recent reviews (17-19) were also examined, yielding two further publications, and the details of one recently published study were obtained directly from a coauthor. …