Pilates is really good - and makes your core feel strong and you feel leaner - it helps you loose inches.
But if you're looking for something a little less strenuous on your back you might want to try exercises on the stability ball. It actually feels great on my back.
I had a former love for Pilates but now I'm switching to the ball. Let me know if you have any questions!
Pilates will help you develop strength in you back, but you might actually find that it puts strain on your back at first. I know when I started I had to do the beginner or modified poses because my back and abs weren't strong enough.