DEAN KARNAZES

AGE: 44
OCCUPATION: Ultramarathon runner, author
NUMBER OF TIME COVERS: 0
PREVIOUS APPEARANCES ON THE TIME 100: 0

PRO: A staunch advocate for healthy and active living, Karnazes last year completed 50 marathons in 50 states in 50 days, ending with the New York City marathon, which he completed in three hours thirty seconds. His book, Ultramarathon Man, was the #7 bestselling sports book worldwide in 2005.

CON: Pledged to run home from New York to San Francisco after the Endurance 50, but stopped when he reached St. Louis. The secrets to his success—sleeping less, eating junk food and pushing your body to the point of death—are, obviously, not for everyone.