Study: Virus may contribute to obesity - CNN.com Health

WASHINGTON (AP) -- 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 -- the blank slate of the cell world -- were exposed to a common virus they turned into fat cells. They didn't just change, they stored fat, too.

While this may be a guilt-free explanation for putting on pounds, it doesn't explain all or even most of America's growing obesity problem. But it adds to other recent evidence that blames more than just super-sized appetites and underused muscles for expanding waistlines.