Awwww Little Jerry needs to go on a diet
If you have a yard or can bring him to an enclosed space, I would just let him run around for 5 or 10 minutes a day. If I'm really busy with school or work and can't play outside long, I just bring one of my books outside and let him run around. He literally runs circles.
I don't think a diet is necessary -- just get him off that Cesar and see what happens with just dry food and some good hardy exercise.