Studying the health outcomes of food/beverage taxes and subsidies in countries of different income classifications; a systematic review Consumption of energy dense foods such as intake of sugar sweetened beverages and fast food consumption have been significant contributors to increase calorie intake and higher body weight [1-9], which lead to overweight and obesity. Intake of energy dense foods also associated with other poor health outcomes such as type two diabetes, heart disease and certain cancers The prevalence of obesity has been reaching an alarming stage in some developed countries. and has been rising fast in the rest of the world. The World Health Organization estimated the adults (20 and older) prevalence of overweight (BMI 25) at 1.4 billion globally in 2008, of which obese adults (BMI 30) numbered 500 million; by 2015, these figures are projected to rise to 2.3 billion overweight and of which 700 million obese adults[1]. The simultaneous increases in obesity in almost all countries seem to be driven mainly by changes in the global food system. To alter this trend, strategies for weight maintenance as well as weight reduction must become a higher public health priority [2]. One strategy that has gained considerable attention is the use of targeted taxes, subsidies, or both to influence food purchases [1, 3-7]. The presence of obesogenic food environment, long-term changes in physical activity levels and energy expenditure are also contributory factors for the rising obesity trend [8]. Currently, financial incentives favor the consumption of energy dense nutritive poor foods since it is consistently cheaper, in terms of energy content of a given price, than less energy dense nutritive high foods. The obesity epidemic and growing evidence on the causal relationship between unhealthy diet and increased disease risk have led to renewed emphasis on the public health strategies aimed at improving dietary quality among children and adults. The World Health Organization (WHO) has recommended in their reports the use of fiscal interventions on foods to encourage healthy eating [9-11]. In consistent with the WHO recommendation, presently there is a global interest to the effect of fiscal policy on diet. Governments use taxation and subsidies as fiscal policy instruments to encourage healthy eating behavior. Fiscal interventions have been used as a health promotion strategy. Taxing energy dense nutritive poor foods could create a financial incentive
for consumers to avoid them while subsidizing energy dense nutritive high foods encourage consumers to eat. The evidence of effectiveness of fiscal interventions on food comes from natural experiments, controlled trials and modeling studies. Evidence on fiscal interventions on food to improve health outcome is far from complete [12]. Most of the systematic reviews on fiscal interventions and health outcome focused on controlled trials and modeling studies while few reviews included both modeling and empirical studies. There is no published systematic review only focused on the effectiveness of implemented fiscal interventions (tax/subsidies) on foods and their impact on health. Most of the evidence on effectiveness of fiscal interventions comes from developed countries and the evidence derived from those studies might not be applicable to developing countries. Previous research also highlighted the need to understand the impact of fiscal policy in developing countries Thow et al. (2010). Methods This systematic review set out to answer the following research questions: (1) Is there evidence of the effect of implemented food and beverage taxes and/or subsidies on behavioural or health outcomes? (2) Does evidence of the effect of these differ between countries from different income groups, as determined by the World Bank? To be included in this study the article had to meet all the following criteria: Examined implemented taxes/subsidies at national or local level Examined a tax/subsidy on food or beverages (i.e. general agricultural subsidies were excluded) Published in English language Assessed the effect of the tax or subsidy on health or behavioural outcomes Published in academic or grey literature in English from earliest record to May 2013
Human participants Emergency food relief services (eg free food distribution) were excluded as they provide intermittent or one-off assistance. Given the challenge of changing food habits, it is unlikely that such intermittent nutrition interventions would have sustained impacts nutritional intake. To be eligible for this review, a study must have reported validated measures of at least one of the following as a primary outcome (i) anthropometric measures e.g. body weight, body mass index, waist circumference, (ii) nutrition intake/food purchases (measured by validated dietary assessment techniques, food purchasing, or biomarkers) (iii) any measures of physical health e.g. mortality, morbidity, hospital attendance/admissions or emergency department attendance (iv) pregnancy related outcome e.g. rate of preterm delivery, or low birth weight, mean birth weight (v) child growth and development measures e.g BMI percentile of age. The search strategy was designed to be used in the following databases: Medline, PubMed, EconLit and PAIS, Global Health, Global Health Library, EconLit, Pais international, Science Citation Index, Social Science Citation Index, Conference Proceedings Citation Index Science & Conference Proceedings Citation Index Social Science & Humanities. It was developed with the help of a qualified librarian. Search strategy is attached. Ethical statement An ethics review was not required for this work.
7604 records identified through database searches Remove duplicates Remove animal studies 6191 records identified 5694 citations judged irrelevant by titles 503 potentially relevant on the basis of title 151 abstracts retrieved for further assessment 352 excluded on the basis of abstract (most because they did not assess the health outcome of a defined tax/subsidy 121 excluded on the basis of full text review 29 identified for final review 1 article removed due to non availability of full text Data synthesis and analysis All manuscripts from searches were downloaded into an endnote library. Articles were initially selected on the basis of their titles. Those whose abstracts were deemed irrelevant were then excluded. One potentially eligible abstract had to be removed due to non availability of the full
article. It was not possible to get this article through the interlibrary loan or by contacting the author. 29 full text manuscripts were identified as potentially relevant papers from the initial screening, then the final screening was undertaken by two independent authors (AA and NT) to check whether it met out full list of inclusion and exclusion criteria. For the purpose of analysis, studies were classified according to: (i) the outcome assessed, such as the effect on food consumption, body weight or health outcome (ii) whether or not they were peer reviewed. Any unintended outcomes due to tax or subsidy will also be recorded. Data extraction: Author and year of publication Year of study Location of study World Bank income group of country Type of study Intervention type Intervention target population Duration of intervention Outcome measure Study population Sample Size Outcome data source Major findings Other effects
Peer reviewed article (Y/N) References 1. Faith, M.S., et al., Toward the reduction of population obesity: macrolevel environmental approaches to the problems of food, eating, and obesity. Psychological Bulletin, 2007. 133(2): p. 205. 2. Nestle, M. and M.F. Jacobson, Halting the obesity epidemic: a public health policy approach. Public Health Reports, 2000. 115(1): p. 12. 3. Finkelstein, E., et al., Pros and cons of proposed interventions to promote healthy eating. American Journal of Preventive Medicine, 2004. 27(3): p. 163-171. 4. Kuchler, F., A. Tegene, and J.M. Harris, Taxing snack foods: Manipulating diet quality or financing information programs? Applied Economic Perspectives and Policy, 2005. 27(1): p. 4-20. 5. Jacobson, M.F. and K.D. Brownell, Small taxes on soft drinks and snack foods to promote health. American Journal of Public Health, 2000. 90(6): p. 854. 6. Marshall, T., Exploring a fiscal food policy: the case of diet and ischaemic heart disease. BMJ: British Medical Journal, 2000. 320(7230): p. 301. 7. Cash, S.B., D.L. Sunding, and D. Zilberman, Fat taxes and thin subsidies: prices, diet, and health outcomes. Acta Agriculturae Scand Section C, 2005. 2(3-4): p. 167-174. 8. Swinburn, B. and G. Egger, The runaway weight gain train: too many accelerators, not enough brakes. BMJ: British Medical Journal, 2004. 329(7468): p. 736. 9. WHO, Global strategy on diet, physical activity and health.. 2004. 10. WHO, 2008 2013 action plan for the global strategy for the prevention and control of noncommunicable diseases. 2009. 11. WHO, Draft action plan for the prevention and control of noncommunicable diseases 2013 2020 2013. 12. Cash, S. and R.D. Lacanilao, Taxing food to improve health: economic evidence and arguments. Agricultural and Resource Economics Review, 2007. 36(2): p. 174.