Virus may be partly to blame for obesity

In the buffet of reasons for why Americans are getting fatter, researchers are piling more evidence on the plate for one still-controversial cause: a virus.

New research announced Monday found that when human stem cells were exposed to a common virus they turned into fat cells and began storing fat.

This adds to other recent evidence that blames some expanding waistlines on more than just super-sized appetites and underused muscles.

For several years, researchers have looked at a possible link between obesity and this common virus, called adenovirus-36, from a family of viruses that cause colds and pinkeye in people. They had already found that a higher percentage of fat people had been infected with the virus than people who were not fat.

But ethical restraints kept researchers from exposing people to the virus to see what happened. So they did what would be considered the next best thing, said Nikhil Dhurandhar, who headed the research at the Pennington Biomedical Research Center in the Louisiana State University system.

They took fat tissue from people who had liposuction, removed adult stem cells from the tissue and exposed the cells to the virus in the lab. Adult stem cells can turn into different types of specialized cells to help the body heal itself.

More than half of the stem cells exposed to the virus turned into fat cells and accumulated fat, while only a small percentage of the non-exposed stem cells did the same, said researcher Dr. Magdalena Pasarica, who presented the results Monday at the American Chemical Society's annual meeting in Boston.

"It's the first time we see an effect in human cells," Pasarica said in a phone interview.

If a viral cause of obesity can be confirmed, a vaccine could be developed to prevent the virus from making some people fat, Dhurandhar said. However, it wouldn't help people who already are obese, he said.

Outside experts are intrigued but worry about people blaming all obesity on viruses.

"The cause for obesity in everyone is the same," said Dr. Samuel Klein, director of the Center for Human Nutrition at the Washington University School of Medicine in St. Louis. "You eat more calories than you burn up."