Lose some weight. Work out. Alot easier said than done though. It takes committment, not just talking about it on an internet forum.
Change things up so you don't get stuck in a boring routine, I'm doing workouts using the Kinect on Xbox360, spending time on the elliptical in hillclimb mode while I watch a hunting show, and jogging when I get a chance. I would say that when you are able to run a half marathon in 2 hours you are getting close to "sheep shape".
You need to mix in plenty of hills and burst though, not just steady running.