A new study claims the common cold virus could be responsible for making people obese.
An American team led by Dr Magdalena Pasarica, from the Pennington Biomedical Research Center at Louisiana State University, Baton Rouge, have found a particular gene in the virus that promotes weight gain.
And the study shows that 30% of obese people carry the virus, compared with 11% of average-weight individuals.
Dr Pasarica said: "We're not saying that a virus is the only cause of obesity, but this study provides stronger evidence that some obesity cases may involve viral infections.
"We would ultimately like to identify the underlying factors that predispose some obese people to develop this virus and eventually find a way to treat it."
Tam Fry, board member of the National Obesity Forum and chairman of the Child Growth Foundation, said: "I think you have to take this research seriously and it would be wrong to dismiss it as nonsense.
"But it would be absolutely absurd to assume that obesity is something you 'catch' and cannot be helped.
"The crucial message is that whatever you do you must balance energy in with energy out. If you eat more than you burn, you'll get fat."