Coca-Cola will roll out a lower-calorie version of Coke in Britain with a third less sugar, pitching it as a response to a government campaign to fight obesity.

A can of Coca-Cola Life is 89 calories, compared to 139 calories for traditional Coke, and is sweetened with a blend of sugar and stevia leaf extract, a naturally sourced sweetener.

Coca-Cola Life was first piloted in Argentina and Chile last year. This is its first entry into Europe.

The new version of the popular drink will go on sale in Britain in the fall, with a distinctive green can to distinguish it from the original Coke.

In Britain, Coca-Cola signed up for the government's controversial responsibility deal, which encourages companies to take steps that will improve public eating habits. The company said the new product will move it closer to the goal of reducing the average calories per litre in its range of sparkling drinks by five per cent by the end of 2014.

"We were early signatories to the U.K. government's responsibility deal and, as we work with others across society to address the public health challenge of obesity in the U.K. and across Europe, we will continue to take actions that help people balance their lifestyles," said James Quincey, president of Coca-Cola Europe.

Some fans hate stevia

But healthy eating advocates say Coca-Cola Life cannot be considered healthy. A 330ml can will still contain 22.1 grams of sugar – 25 per cent of an adult’s guideline daily amount. That’s down from 35 grams in regular Coke.

Coke also sells two products with much lower calorie counts – Diet Coke and Coke Zero.

Stevia, an extract from a South American plant, is already used in the company's Sprite and Glacéau vitamin water. But it also has detractors.

Fans of the drinks say the stevia alters the taste and have inundated Vitaminwater's Facebook page with complaints. Most are asking that the company bring back the old formula.

Coca-Cola Co. changed the formula for its full-calorie Vitaminwater in May, sweetening the drinks with a mix of sugar and stevia.