Academics at research firm RTI International, Duke University and the US Department of Agriculture published in the American Journal of Agricultural Economics, found that reducing consumption of sugary drinks by imposing a sugar tax was likely to lead consumers to seek those calories elsewhere by increasing their consumption of calories, salt and fat from untaxed foods and beverages.
“Instituting a sugary beverage tax may be an appealing public policy option to curb obesity, but it's not as easy to use taxes to curb obesity as it is with smoking,” said Chen Zhen a research economist at RTI, and the paper’s lead author.
“Consumers can simply substitute a taxed high-calorie food for an untaxed one. And as we know, reducing calories is just one of many ways to promoting healthy eating and reducing nutrition-related chronic disease.”
In January this year the campaign group Sustain called on the chancellor, George Osborne, to impose a duty of around 20p a litre on sugary drinks.
The move was also backed by a further 61 organisations, including the Association for the Study of Obesity, the Association of Teachers and Lecturers and the Centre for Food Policy at City University, London.
It was claimed that the tax would raise £1bn, which could be spent on improving children's health, possibly by providing free school meals.
However, British Soft Drinks Association director general Gavin Partington said soft drinks only accounted for 2% of the calories in the total diet and would not address the “complex issue” of obesity.
'Hit poorer families hardest'
Food and Drink Federation director of communications Terry Jones dismissed the plan, claiming the tax would hit poorer families hardest – a point that appears to be backed up by this latest study.
Researchers also examined the differences in purchasing behaviour between lower- and higher-income households. Compared with higher- income families’ purchases, the food and beverages bought by poorer families tend to be higher in calories, fat and sodium content on average.
“Because lower- income families tend to buy more sugary soft drinks than higher income families, they would more readily reap the health benefits of reduced sugary beverage intake,” Zhen said. “However, they would also pay more in beverage taxes, making it a regressive tax.”
Last year the Danish government abandoned its plans to introduce a sugar tax as the weight of evidence mounted against using fiscal measures to improve public health.