The success of the sugary drinks tax has shifted public opinion, policy makers need a more open-minded approach to evidence, say Susan Jebb and Theresa Marteau
In an editorial in the Financial Times on 8th July 2019 John Thurnhill argued that Boris Johnson’s instincts on so-called “sin taxes” may be right and we should avoid “needless government intervention” but that in the case of sugary drinks the benefit of fiscal intervention is clear. The soft drink levy has greatly accelerated the reformulation of sugary drinks and led to a marked change in consumer behaviour, through greater awareness of the health harms of sugary drinks, shifts in the availability and marketing of soft drinks as well as the impacts of price rises on purchasing behaviour, together leading to marked reductions in the sugar consumed in drinks.  But this direct evidence of effectiveness has only accumulated in the aftermath of the policy.
The challenge for public health is that for new policies to be introduced requires a more open-minded approach to the nature of evidence—combining plausible mechanisms, modelling and case-studies from other countries or similar scenarios. So, what might be the next steps for fiscal interventions to prevent obesity?
At present diverse voices are proposing an assortment of new measures—ranging from extending the soft drink industry levy (SDIL) to milkshakes or fruit juice through to a meat tax to encourage more sustainable eating habits. We conducted the first modelling exercise of the likely impact on BMI and the prevalence of obesity of a price rise in three sets of high-sugar snacks; confectionery, biscuits, and cakes.  We estimated that increasing their price by 20% would lead to fewer high-sugar snacks being purchased, with consequent reductions in BMI of a magnitude more than double the modelled impact of a similar price rises in sugary drinks. The effects were also greatest in low-income households classified as obese, suggesting that such a price rise would have greatest benefit amongst households where obesity rates are highest.
To date, public policy to improve the nutritional quality of the food supply has relied heavily on reformulation. It’s worked well for sugary drinks, where reformulation to produce very similar, but low sugar products results in a highly acceptable alternative. But the same is not so for many other high sugar snacks, especially confectionary, and the only real option to cut sugar is for people to eat less. Previous efforts to encourage smaller portions have decreased the size of individual bars of chocolate, but coincided with the growth of so-called “sharing bags” with no evidence of any substantive decrease in overall consumption.  It’s time for a new approach.
Price rises on unhealthy products—tobacco, alcohol, and sugary drinks—are some of the most effective, but least popular interventions for improving health.  However, there has been an interesting shift in attitudes to taxing sugary drinks with the majority of respondents in a recent survey supporting its introduction when the proceeds were to be used to improve children’s health.  Hypothecation it is argued increases the acceptability of fiscal policies.  Or the shift in attitudes may reflect a growing awareness of the threat that obesity poses to health, particularly that of children. The evidence we present here—that price increases on high sugar snacks could be effective in tackling obesity—could increase public support for policy action. 
The views of the public and policy-makers will also be shaped by the words and actions of those who produce high-sugar snacks. Business in general oppose such measures since profits will be hit by the introduction of fiscal policies to reduce consumption. Voluntary targets to encourage reformulation or reductions in portion size also impose costs on businesses and are likely to disadvantage the companies who take the most decisive action. Businesses committed to improving diet quality and tackling obesity should welcome interventions that create a level playing field across the market to address overconsumption of high sugar snacks.
The evidence is stacking up, but it remains to be seen when it will overcome the natural instincts of business and policymakers to let the market shape what we eat.
Susan Jebb is a nutrition scientist and professor of diet and population health in the Nuffield Department of Primary Care Health Sciences, University of Oxford. She is a National Institute for Health Research (NIHR) senior investigator and a member of the Scientific Advisory Committee on Nutrition. She leads the NIHR Oxford Biomedical Research Centre (BRC) and Collaboration and Leadership in Applied Health Research and Care (CLAHRC) Oxford themes on diet and obesity. Her research programme focuses on dietary interventions that might be effective to help people lose weight or reduce the risk of obesity related diseases.
Competing interests: See accompanying research paper and previous opinion piece
Theresa Marteau is Director of the Behaviour and Health Research Unit in the Clinical School at the University of Cambridge, and Director of Studies in Psychological and Behavioural Sciences at Christ’s College, Cambridge. Her research interests include: development and evaluation of interventions to change behaviour (principally diet, tobacco and alcohol consumption) to improve population health and reduce health inequalities, with a particular focus on targeting non-conscious processes; risk perception and communication, particular of biomarker-derived risks, and their weak links with behaviour change; and acceptability to publics and policy makers of government intervention to change behavior. Current research in her group is funded by Wellcome Trust.
Competing interests: See accompanying research paper
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