Can a virus make you fat?

A common cold-like virus may increase body fat

By BBC News Online's Matt McGrath

Researchers in the United States say some people's weight problems might be caused by a common cold virus.

Experiments with animals suggest that AD-36, a virus which causes coughing, sneezing and cold-like symptoms, interferes with the normal process of absorbing food energy and converts far more of it into fat.

There have been five other viruses to date that have shown an impact on obesity but this is first human one

Dr Nikhil Dhurandhar

Dr Nikhil Dhurandhar and colleagues from the University of Wisconsin injected chickens and mice with AD-36.

Despite being fed the same amounts of food as a control group, the test subjects gained small amounts of extra weight.

But the scientists found that the animals had put on large amounts of body fat, almost 2.5 times more than normal.

This work has been published in the International Journal of Obesity.

Dr Dhurandhar told BBC News Online that in unpublished research he had also used the same virus to cause obesity in Marmoset monkeys.

And he said that while the research was not definitive proof it indicated that this virus might have a similar impact on humans.

"There have been five other viruses to date that have shown an impact on obesity but this is first human one. It's suggestive of a direct effect in people," he said.

More research needed

Screening blood samples for signs of the virus, Dr Dhurandhar said that about 30% of obese people had contracted AD-36 compared to 5% for lean people.

"We're not saying that all obesity is due to this virus - but there might be a percentage of people in whom this virus might be contributing to their obesity," he said.

Other scientists called for more definitive research. Professor Nick Finer, director of the Centre for Obesity Research, Luton and Dunstable Hospital in Luton, UK, said the work was very interesting.

A virus like this was found in 30% of obese blood samples

"We can't dismiss the findings out of hand but there's a large gap between this experimental evidence and going on to say that viruses are a common cause of obesity in man."

Ethical considerations mean that virus experiments on people are not possible, said Dr Dhurandhar, but he will keep on collecting indirect evidence.

"We want to look at people who have the virus, and look at them again in two to five years" he said.

Vaccines against this virus might one day be possible said Dr Dhurandhar, but he believed that the biggest impact of his work would be to increase the acceptance of obesity as a disease.