Dr Mike Rayner, Principal Investigator at the Oxford Martin Programme on the Future of Food, has directed new research into the impact of sugary drinks on obesity. The findings from the British Heart Foundation Health Promotion Research Group at the University of Oxford and the Centre for Food Security at the University of Reading have published their findings in the British Medical Journal.

The study has found that the number of obese adults in the UK could be reduced by 180,000 with a 20% tax on sugary drinks. The tax could raise over £275 million for the Treasury.

A tax on sugary drinks has been proposed as a public health measure for a number of reasons. Sugary drinks (soft drinks with added sugar such as fizzy drinks, squashes and cordials) have been shown to increase the risk of obesity, diabetes, cardiovascular disease and tooth decay.

They only suppress appetite weakly, so consuming fewer sugary drinks is unlikely to result in an increased intake of other sources of calories. There are no beneficial nutrients in sugary drinks, so reducing consumption will not remove important nutrients from the diet. And from a legislative perspective, sugary drinks can be clearly defined, the researchers say.

The scientists used a large survey of shopping preferences of families in the UK to estimate how purchases of sugary drinks would change in response to a 20% increase in their price. They also looked at how purchases of other drinks, such as orange juice, milk and diet drinks, might change in response to the price change. They then used this information to estimate the change in average calorie intake and obesity.

The research suggests that purchases of sugary drinks would reduce by around 15% with people mainly switching to diet drinks and tea and coffee. The expected reduction in energy intake is 28 calories per person per week.

The researchers estimate this would reduce the number of obese adults across the population by 180,000 (with the number likely to be in a range from 110,000 to 250,000), or 1.3% of all obese adults in the UK.

The impact on obesity is likely to be much greater in younger adults who drink larger quantities of sugary drinks than older adults. On average, people aged 16-29 years drink around 300 ml of sugary drinks per day, compared to just 60 ml in those aged over 50.

The Oxford and Reading research team also investigated the effect on obesity among different income groups. The study indicates that there would be similar health gains across all groups, looking at the thirds of the population with lowest, middle and highest incomes.

The estimated increase in the amount people would spend on drinks would be an extra 9p a week (or under £5 a year) for those in the lowest income group. It would be 6p per week for those in the highest income group. The increase in expense is small as most people would react to the tax by purchasing fewer sugary drinks, the study suggests.

Dr Mike Rayner says: ‘Taxes on sugary drinks are moving up the political agenda in the UK and abroad. Increasingly, governments are recognising the health burden imposed by sugary drinks and that this burden can be reduced by measures to discourage consumption. Because sugary drinks do not provide any beneficial nutrition there are no downsides to reducing consumption levels in the UK using taxation.’

You can read the full news release on the University of Oxford website and the full report is available at www.bmj.com