8. Catching the wrong virus
Yet another reason to wash your hands properly: It’s your best bet to avoid catching adenovirus-36, a human virus that causes upper respiratory infections with symptoms like those of a flu or a cold, and may also make you prone to weight gain. The virus appears to convert adult stem cells into fat cells and is more prevalent in the obese. About 30 percent of obese people in the U.S. have been exposed to it, compared to 11 percent of normal-weight people, according to one screening. Animals that were infected with adenovirus-36 gained up to four times as much weight as those without it.