Zero sugar - zero effects? Why 'diet' drinks might not work

New Year dieters may be in for a disappointment after researchers concluded that sugar-free "diet" drinks do not help with weight loss.

A paper by scientists at Imperial College London says there is no proof that the likes of diet colas help weight-watchers or help prevent obesity-related diseases such as Type 2 diabetes.

Indeed, they warn, such fizzy drinks might even cause people to gain weight.

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Diet drinks are sold as healthy versions because they have far fewer calories than "full-fat" versions, but the researchers, who reviewed dozens of studies going back some three decades, say they could make people crave food because they trigger sweet receptors in the brain, the Daily Telegraph reports.

That could lead to overindulging on both food and also the drinks themselves, especially given the perception they are healthier.

"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," said Professor Christopher Millett, senior investigator from Imperial’s School of Public Health, which worked alongside Brazil's University of Sao Paulo and the Federal University of Pelotas.

The British Soft Drinks Association, however, said the industry was being "demonised without evidence", while Professor Susan Jebb, the government's obesity advisor, said switching to less sugary versions of fizzy drinks was a "step in the right direction", although drinking tap water was always the healthiest and most environmentally friendly option, The Independent reports.

Artificially-sweetened drinks account for a quarter of the sugary-beverages market worldwide, but they are not taxed or regulated to the same extent as their full-sugar counterparts, perhaps because they are perceived as healthier alternatives, the researchers claim.

They also criticised previous studies funded by the fizzy drinks industry, which they said were more likely to find a positive link between low-calorie drinks and weight loss.