A good runner in middle school and high school, Dean Karnazes quit running until he was 30. The night of his 30th birthday, he ran 30 miles. He hasn't looked back since. Karnazes is now one of the most famous ultramarathon runners ever. He's won Badwater (over 100 miles in Death Valley, don't even think about it, it's invitation-only), and he's competed in a marathon at the South Pole in temperatures around -40 F. He is perhaps most famous for the 50/50/50 marathons he ran – 50 marathons, in 50 states, in 50 days – to raise awareness for childhood obesity.