In the UK, sugar-sweetened drinks may account for half of the excess calories consumed per day by children, while one in four British adults is obese, according to a 2013 report from the United Nations. Financial measures, alongside wider strategies, are one option but there is limited evidence on the effectiveness of such measures on either the sale or consumption of SSBs.
In 37 Jamie's Italian outlets, 10p was added to the price of SSBs, starting in September 2015.
In addition, fruit spritzers (fruit juice mixed with water) were added to the main non-alcoholic beverage menu which also explained the decision to implement the levy and that proceeds would go directly to the Children's Health Fund which supports children's health initiatives.
"We are delighted that this independent evaluation confirms that introducing such a levy has led to a significant decline in sales of sugary drinks in participating restaurants and we note the Children's Health Fund is also beginning to create real, lasting change to the lives of children around the United Kingdom through supporting projects to provide them with safe accessible drinking water and healthy food during the holidays", explains Prof.
But the study did not look at any other restaurant chains to compare sales figures.
"Sugar taxes are now extremely popular policies to curb obesity rates and improve population diet", said Steven Cummins, senior author of the study and a professor of population health at the London School of Hygiene & Tropical Medicine.
The study also showed there was a general decrease in the number of soft drinks sold per customer, including diet drinks and bottled waters.
Sales of fruit juices had increased by 22% six months after the changes were introduced. Sales of diet cola and bottled waters also declined. It was added to all non-alcoholic sugar sweetened drinks available in 37 of the restaurant's United Kingdom outlets.
Dr. Laura Cornelsen, Assistant Professor in Public Health Economics and MRC Career Development Fellow at the London School of Hygiene & Tropical Medicine, co-led the study.
Professor Cummins said: 'A possible reason for this decline could be that more people were choosing tap water, but data on tap water orders was not available as it was not recorded on the restaurant's sales system.
But she said there was a disappointing lack of data on alcohol sales, which could have increased over the same period. For example, how big a role did the menu change or the text introducing the levy play?
In the year before the charge the chain sold more than 2million non-alcoholic drinks, of which 38 per cent were sugar sweetened. Further research is needed to work out how such levies can best be used in different settings and circumstances.
"Obesity, type 2 diabetes and cardiovascular disease are among the most pressing global health challenges facing the world today. Population interventions of this sort could be vital in combating them".
When Mr Oliver introduced his 10p levy two years ago, he said: 'I was born into the restaurant industry and I truly believe that by joining together on this issue we not only send a powerful and strong message to government but we also have the potential to make a longlasting legacy that could ripple across the world.