It is a far cry from the good old British cuppa. The Coca-Cola Company is launching a new tea developed with Nestlé that speeds up the metabolism so much it is called "negative calorie".

The sparkling green tea, Enviga, is intended to be served cold and is designed to appeal to weight-loss enthusiasts in the US. Coke says drinking three servings of Enviga a day will burn between 60 and 100 calories more than normal. The developers say it contains more epigallocatechin gallate, an antioxidant known to increase energy burning, than other green teas.

"It's a positive step people can take as part of a balanced lifestyle - like taking the stairs," said John Hackett, Coke's senior vice-president for marketing.

Sales in Europe are planned next year.