To help lose weight, you need to maintain your blood sugar during and after exercise. That means a good hydration drink during the ride, and a recovery drink after the ride. There are lots of different choices for both - I use accelerade during the ride, and endurox after, but you may need to try a few to find one that works. If you are okay with milk, lowfat chocolate milk is a pretty good recovery drink.
If your blood sugar is up, you will be less hungry after your workouts, and therefore you won't feel the need to eat as much.
Recovery drinks also keep your body from tearing down muscle to replace your muscle glycogen.