I am stocky, want to be lean. Suggestions?

I have been told time and time again how built and stocky I am...football player's build. That's cool and all,but I'm 22 now and I would much rather have a lean physique (think Bale in American Psycho, not Bale in Batman Begins which is where I'm at). If anyone knows of a great workout program I can do or any tips, please let me know. I'm currently doing jogging/sprinting intervals on the treadmill. About 20 minutes a day. Thanks!