CNN has a series of photos showing how the stress of being president takes a physical toll in the form of accelerated aging. Above, a guess at what Obama will look like after 4 years.

The president ages twice as fast while in office, according to a theory advanced by Dr. Michael Roizen, a chief wellness officer at the Cleveland Clinic.

"The typical person who lives one year ages one year," he said. "The typical president ages two years for every year they are in office."