A 30% reduction of sugar in drinks with over 8g of sugar per 100ml and a 15% reduction in drinks with 5–8g of sugar per 100ml could result in 144,000 fewer cases of obesity in adults and children, according to the report.
In the study, researchers modelled three ways that the soft drinks industry may respond to the levy.
These were: reformulating drinks to reduce sugar content; passing some of the levy to consumers by raising the price of sugary drinks; and using marketing to encourage consumers to switch to lower sugar drinks.
However, co-author of the report Susan Jebb said that while levy would have a positive impact, especially on children's health, on its own it cannot solve the obesity crisis.
Cannot solve the obesity crisis
“Once this Bill is passed, we need to consider how to take effective action to reduce other sources of sugar in children's diets, notably confectionery,” said Jebb.
“This has, so far, been relatively overlooked, while hearts and minds have been focused on the soft drink levy.”
Children were the most likely to be benefit from the tax, but the health benefits could be reduced if soft drinks firms responded by increasing the price across their drinks ranges – including zero sugar and diet drinks.
British Soft Drinks Association director general Gavin Partington said the report was ultimately flawed.
“The problem with this modelling is that it is based on the flawed concept that obesity can simply be attributed to calorie or sugar intake per se and consumption of one product in particular, rather than overall lifestyle and diet,” said Partington.
“This error is plain to see given that sugar intake from soft drinks has been declining for several years now. There is no evidence worldwide that a tax on soft drinks has had an impact on levels of obesity.”
Some retailers have started to reduce the sugar in their own-label drinks, ahead of the implementation of the tax in April 2018.
Tesco reduced the sugar by up to half in some of its drinks – including its own-label cola. Meanwhile, Waitrose has reduced sugar in most of its own-label products, including drinks, cereal and yogurts.