Obesity has been linked with genetics as well as environmental factors. Although previous research linked obesity to a virus, this is the first time that link has been fully explained.

Obesity is a dangerous condition which is linked to the so-called lifestyle diseases like type 2 diabetes mellitus, hypertension, obstructive sleep apnea, nonalcoholic steatohepatitis, heart disease, poor self-esteem, and a lower health-related quality of life. Last year a report in the Journal of American Medical Association revealed increasing obesity and overweight rates among Americans.

A person having a Body Mass Index of 25 or above is considered overweight, while those having BMIs of 30 or above are obese.

Sedentary lifestyle practices coupled with a shift in diet to junk foods are the main reason behind this explosion of overweight or obese population. The World Health Organization has declared obesity as a global epidemic having major health implications in 1997. It estimated that some 2 billion people worldwide are obese or overweight.

In the present study researchers were able to demonstrate that stem cells exposed to adenovirus-36 (Ad-36) are converted into fat cells and what is more they have the so-called "fattening effect." Adenovirus-36 is known to cause respiratory and eye infections.

Researchers at the Pennington Biomedical Research Center had already proved the increased existence of adenovirus-36 in obese individuals as compared to normal weight ones. The mechanism behind this finding is explained in this study to be reported at the national meeting of the American Chemical Society in Boston.

Stem cells that were not exposed to adenovirus-36 did not develop into fat cells lending credence to the theory that obesity may be a viral condition and could be prevented by taking anti-viral medication.

"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," explained lead researcher Dr Magdalena Pasarica. "Not all infected people will develop obesity. 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."

The researchers exposed adult stem cells from the fatty tissue to the adenovirus-36 and found the stem cells had converted to fat cells after one week. Cells that were not exposed to the virus did not turn into fat cells. A gene called E4Orfl appears to play a key role in triggering fat deposition, the researchers added.

The infection with the virus could also explain the increasing trend of childhood obesity because children are the ones who get frequent respiratory infections.

Last month a study by researchers at the Johns Hopkins University in Baltimore had predicted that three-quarters of the population in the United States will be battling flab by 2015.

Some 24 percent of children are predicted to be overweight or obese by 2015. Childhood obesity is a growing menace to the society. In recent years, this epidemic has risen alarmingly.

Last May the American Academy of Pediatrics had recommended that doctors pay attention to the physical activity of their child patients.  Physicians should encourage "healthy nutrition, reducing sedentary time, and increasing physical activity levels while providing education and health supervision about regular physical activity and reduced sedentary time to families in their practices," it had stated.

Schools have already banned or limited the sale of fizzy drinks following a deal between major companies and the Alliance for a Healthier Generation in May 2006. The Alliance is a joint venture of the William J. Clinton Foundation and the American Heart Association.

However despite all these measures, child obesity is continuing to grow at a fast pace that is concerning authorities. The review found that obesity rates have been registering a 0.2 to 0.8 percent annual increase over the last few years. The review used data from NHANES, BRFSS, Youth Risk Behavior Surveillance System and National Longitudinal Survey of Adolescent Health.

The new study offers another avenue to beat fat. However these findings will need to be substantiated in human trials. But early research by Dr Nikhil Dhurandhar and Dr Magdalena Pasarica had found 30 percent of obese individuals were infected with adenovirus-36 while only 11 percent normal weight people had had this infection.

The present study linking a virus to overweight and obesity may provide researchers with a clue needed to explain the mechanism behind obesity. Concurrently it also offers drug companies a chance to find a drug to beat the adenovirus infection and thus battle obesity.

Nevertheless consumers must be aware that the key to fighting obesity lies in maintaining an active lifestyle and eating a balanced diet regardless of the other factors involved.