Researchers advice people to drink water instead, as too much of fizzy drinks can change the metabolism of the body. This means that muscles begin to use sugar for energy, instead of burning fat.
Dr Hans-Peter Kubis, who led the research at Bangor University, said: "Our results give a stark warning against regularly drinking sugar-sweetened drinks. Not only can regular sugar intake acutely change our body metabolism; in fact it seems that our muscles are able to sense the sugars and make our metabolism more inefficient, not only in the present but in the future as well. This will lead a reduced ability to burn fat and to fat gain. Moreover, it will make it more difficult for our body to cope with rises in blood sugar."