The rats who drank fizzy drinks also showed signs of fat accumulating around their organs, a symptom of chronic obesity.Levels of the hunger hormone ghrelin were “significantly higher” after the rats had had a carbonated drink.Tam Fry, of the National Obesity Forum, told the Mail on Sunday: “The Department of Health must now curb the use of any chemicals that impinge on health and that should include carbon dioxide if this effect is replicated in further studies.”Subsequent tests on human volunteers found that those who drank sparkling water at breakfast had ghrelin levels six times higher than those who had still water.Gavin Partington, director-general of the British Soft Drinks Association, said the study was “bad science” because the outcomes for humans may not be the same as those for rats. “There is no body of scientific evidence that carbon dioxide contained in soft drinks – or even beer – causes increased hunger or obesity,” he said. The experiment used fizzy drinks Want the best of The Telegraph direct to your email and WhatsApp? Sign up to our free twice-daily Front Page newsletter and new audio briefings. Fizzy water could be a cause of obesity, according to a new study. Academics at Birzeit University in the Palestinian West Bank found that rats who were given fizzy drinks including zero-calorie versions put on weight, while those who drank flat liquid did not. They said that the carbon dioxide in the drinks encouraged the rats to eat on average 20 per cent more.