Sugar-free and diet drinks are not helpful for weight loss and could even cause people to pile on the pounds, researchers at Imperial College in Britain have claimed.
A review of dozens of studies dating back 30 years found that there is no solid evidence that sugar-free alternatives prevent weight gain, type 2 diabetes or help maintain a healthy Body Mass Index. (BMI)
Although artificially-sweetened beverages contain fewer calories than sugary versions, researchers say they still trigger sweet receptors in the brain, which may make people crave food.
Coupled with the fact that most people view diet drinks as healthier, it could lead to over-consumption, the researchers argue.
"A common perception, which may be influenced by industry marketing, is that because 'diet' drinks have no sugar, they must be healthier and aid weight loss when used as a substitute for full sugar versions," said Professor Christopher Millett, senior investigator from Imperial's School of Public Health.
"However we found no solid evidence to support this. Far from helping to solve the global obesity crisis, artificially-sweetened beverages may be contributing to the problem and should not be promoted as part of a healthy diet."
The authors claim that previous studies which found diet drinks were helpful should be discounted because they were funded by the drinks industry.
However the British Soft Drinks Association said that it was wrong to target sugar-free drinks, because they helped people maintain a low calorie diet.
Gavin Partington, BSDA Director General, said: "At a time when we are trying to encourage people to reduce their overall calorie intake it is extremely unhelpful that products which contain no sugar, let alone calories, are demonised without evidence.
"It's worth bearing in mind that the UK soft drinks sector is the only category in which sugar intake is consistently falling year on year - over 17 per cent since 2012."
Professor Susan Jebb, the British Government's advisor on obesity, said that sugar was a major risk factor for obesity, type 2 diabetes and tooth decay and said switching to artificially sweetened drinks was a helpful step.
"For people seeking to manage their weight tap water is without question the best drink to choose, for health and the environment, but for many people who are used to drinking sugary drinks this will be too hard a change to make," said Jebb, Professor of Diet and Population Health at the University of Oxford.
"Artificially sweetened drinks are a step in the right direction to cut calories."
Tom Sanders, professor emeritus of Nutrition and Dietetics, at King's College London, added: "The conclusion that reduced sugar or sugar free drinks should not be promoted or seen as part of a healthy diet seems unwarranted and likely to add to public confusion."
Dr Alison Tedstone, chief nutritionist at Public Health England, said swapping to low or no sugar drinks "goes some way to managing calorie intake and weight", especially for young people.
"However, maintaining a healthy weight takes more than just swapping one product for another," she added. "Calories consumed should match calories used, so looking at the whole diet is very important."
The review was published in the journal PLOS One.