Obesity, and its control, is high on the public health agenda. Recently the Lancet published a series of important papers on the science and social science of obesity and its prevention. According to conservative estimates the projected obesity trends in the UK to 2030 imply 5,450,000 new cases of diabetes, 330,000 cases of coronary heart disease and stroke, and 87,000 cancers leading to an overall loss of 2.2 million quality adjusted life years in the population, all this costing almost £2bn per annum extra in health service costs.

Another paper in the series set out what we currently know about the emerging evidence on the effectiveness and cost-effectiveness of interventions for adults and children based on work from Australia. The good news is that fully eight of the 20 interventions assessed were cost-saving. At the top of that list, and the intervention that is projected to have by far the largest health impact, was a 10% tax on unhealthy foods and beverages.

Hungary and Denmark have both introduced so-called “fat taxes” on certain products and they are being debated across the developed world. In England, in response to the Danish tax, the Prime Minister said “Don’t rule anything out, but let’s look at the evidence.” Andy Burnham speaking on Question Time was more negative and did seem to rule it out on the grounds that a tax would be regressive, penalising the poor for whom food is a much higher percentage of household budgets.  This of course, assumes that a tax wouldn’t work well at changing what we buy. Whether this judgement is correct depends on many things, including: exactly how a tax is levied (for instance on ingredients or products), how comprehensive it is, and what substitutes are available.  This in turn depends on non-economic factors, such as the ability to cook, the availability of substitutes in local food markets, time constraints and, not least, social norms and culture. Relative prices between some foods and others could also be changed in other ways, such as reform of the Common Agricultural Policy. An alternative approach would be to consider subsidies for “good” foods rather than taxes on “bads.” For example, recent research has shown that some foodstuffs, such as nuts, fruit, and yoghurt are associated with weight loss despite increased consumption. 

Any intervention that changes prices could have knock-on effects, so much thought needs to be given to design. In the United States, the tax debate has focused on carbonated drinks. Whilst modelling has shown that moderate tax increases would reduce calorie intake and raise revenue for public health programmes, this has been countered by other work that argues such a tax could distort behaviour with unfavourable effects, shifting consumption to close – and potentially problematic – substitutes, such as alcohol.

So, as the Lancet evidence paper itself makes clear the science behind the effects of levying a fat tax are not clear cut. Deciding whether, and if so how, to change the relative prices of foodstuffs and beverages that are associated with obesity therefore requires much thought and analysis, not knee-jerk reactions for or against.  So, what does the government’s recent policy statement, Healthy Lives, Healthy People: A call to action on obesity in England, say about this thorny and important issue in its chapter on the evidence for obesity interventions? Absolutely nothing. You will search in vain throughout the document for any mention of tax, subsidies, or price as a potential lever in tackling obesity in England, even to dismiss them. It seems the Department of Health has ruled out fat taxes, even if the Prime Minister hasn’t.

David Buck is senior fellow, public health and inequalities at The King’s Fund

This blog also appears on the King’s Fund website at http://www.kingsfund.org.uk/blog/