Researchers 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 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 per cent 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.
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 per cent 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 300ml of sugary drinks per day, compared to just 60ml in those aged over 50.
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"Sugar sweetened drinks are known to be bad for health and our research indicates that a 20 per cent tax could result in a meaningful reduction in the number of obese adults in the UK," said Dr Adam Briggs of the British Heart Foundation Health Promotion Research Group at Oxford University, and joint first author of the study.
"Such a tax is not going to solve obesity by itself, but we have shown it could be an effective public health measure and should be considered alongside other measures to tackle obesity in the UK," Briggs said.
"Because sugary drinks do not provide any beneficial nutrition there are no downsides to reducing consumption levels in the UK using taxation," Rayner said.
The study was published in the British Medical Journal.