Description: New research is bolstering the theory that obesity may stem, a least in part, from a common virus -- one that helps create new, heftier fat cells.

The roots of obesity are probably complex and various, the U.S. team stressed. However, their lab tests showed that exposure to adenovirus-36 (Ad-36), which causes respiratory and eye infections, also causes stem cells to develop into fat cells.

This is the first time anyone has identified a viral "fattening effect" in humans, said lead researcher Dr. Magdalena Pasarica, an obesity researcher with the Pennington Biomedical Research Center at Louisiana State University in Baton Rouge.

The same team was also the first to have shown that Ad-36 is much more prevalent among obese people than among leaner men and women. In that earlier work, the virus was spotted among 30 percent of obese individuals compared with just 11 percent of non-obese people.

In the new study, "we took this a step further, a