The answer may surprise you
As reported by CNN.com, researchers have discovered a possible link between obesity and adenovirus-36, a common virus from a family of viruses that cause colds and pinkeye.
The article stresses that most of America's obese population became super-sized the ol' fashion way: eating more calories than they burned. However, when researchers at Pennington Biomedical Research Center exposed the virus to adult stem cells, "More than half the stem cells exposed to the virus turned into fat cells and accumulated fats, while only a small percentage of the non-exposed stem cells did the same."
Although a vaccine may be developed if a viral cause of obesity can be confirmed, scientists don't believe this vaccine will help those who are already obese.