Tuesday August 21 (Foodconsumer.org) -- Common viral infections may be at least partially responsible for the obesity epidemic sweeping through the United States and other countries, according to U.S. scientists, who reported at the 234th national meeting of the American Chemical Society that a gene in a common virus appears to promote obesity.

laboratory studies led by Magdalena Pasarica from the Louisiana State University system and colleagues showed that human adenovirus-36 (Ad-36), an agent that has long been recognized as a cause of respiratory and eye infections in humans, can turn adult stem cells into fat cells.

"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," said Magdalena Pasarica, M.D., Ph.D., the study presenter.

"Not all infected people will develop obesity," she noted. "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."

An early epidemiologic study led by Nikhil Dhurandhar, Ph.D. from Pennington Biomedical Research Center at the LSUS linked a virus to human obesity for the first time, showing that the Ad-36 is more commonly present in obese people than lean individuals, 30 percent versus 11 percent.

The current study found that the virus is not just a possible cause for the obesity epidemic, but it could actually increase the amount of fat in human cells, Pasasrica said.

In the study, the Ad-36 virus was applied to half of the stem cells obtained from fatty tissue from a broad cross-section of patients who have undergone liposuction. The remaining half were not exposed to the virus.

After one week of tissue culturing, the stem cells exposed to the virus developed into fat cells whereas the stem cells that were not exposed did not, the researchers said.

In animal studies, Dr. Dhurandhar's group recently identified a gene known as E4Orfl in the Ad-36 virus that seems involved in causing fat accumulation in infected animals.

Dr. Dhurandhar said the gene, which is now becoming a promising target for future human therapies such as vaccines and antiviral drugs, may be aimed at preventing or inhibiting the obesity virus.

It remains unknown how much this virus attribute to the obesity epidemic. The researchers can't rule out the possibility that other human viruses may also attribute to obesity.  They just don't know how long the obesity-promoting effect of the virus will last.

An early study showed animals with the virus remained obese up to six months after the virus disappeared, said Pasarica.  But she suggested more work in humans is needed.

The researchers are now researching to explain why some infected people develop obesity while others do not.

"In the past two decades, 10 adipogenic pathogens were reported, including human and nonhuman viruses, scrapie agents, bacteria, and gut microflora," Pasarica and Dhurandhar reported in 2007 in Advances in food and nutrition research.

Recently, Christakis, MD, PhD, and James Fowler, PhD. from Harvard University have reported in the New England Journal of Medicine that social network may be partly responsible for obesity epidemic.  People who had more social networking with obese friends are more likely to be obese compared to those who comminuated with only lean friends.

"Obesity is contagious, but you don't catch it by watching your friends eat too much. You catch it the same way you catch a cold--by inhaling or ingesting certain germs," Russell Farris from http://www.potbellysyndrome.com told foodconsumer.org.

Farris and Per Parin published a book called Potbelly Syndrome, illustrating the importance of the rule of some microorganisms in the obesity.

In the United States, about 97 million adults are either overweight or obese, according to national Institute of Health. Obesity has been linked to a range of diseases including Type 2 diabetes, coronary heart disease, stroke, gallbladder disease, osteoarthritis, and other health disorders.

Editor's note: So what is the take-home message?  The finding means that a vaccine may be developed to prevent certain cases of obesity.  But even with a vaccine, you can still become obese as many factors may attribute to weight gain.  The fundamental one is the foods you eat.  So you do not have to worry about what causes obesity as long as you can eat the right amount of the right food.  Remember: controlling intake of calories is not enough.  You need also to know what to eat.