1. Catching one strain of the cold virus

Children exposed to a particular strain of the common cold virus — called adenovirus 36 — are more likely to be obese than those not exposed, according to findings in the journal Pediatrics in September. In a study of 124 children, nearly 80 percent of those exposed were obese. They weighed an average of 50 pounds (23 kilograms) more than kids not exposed.