IdiotsOpposite
Boom, headshot.
Start with running. It's a relatively low maintenance activity that's good for building discipline. I'm regularly running half marathons these days and it's been making me feel much better about myself. I used to have a sedentary lifestyle so if I can do it I'm sure you can (I am also naturally skinny and athletically built, though).
Hm, I'll have to try this. My sister's a cross country and track and field captain, so maybe I can convince her to help me out a bit on the motivation front. Even I can do running.