Biking is great for body conditioning...not to mention how fun it is! I've been going to the gym for the last couple of years for lifting weights and such, and been using the bike for cardial which in turn has helped me decrease my fat %'s.....I started riding earlier this year to give me extra conditioning and have dropped my body fat by 3% over the last 6 months while only losing around a lb a month, which is great for me as I was only wanting to drop around 8 lbs or so. How much weight are you trying to lose? Be careful and try to keep your monthly weightloss to a minimal as you don't want to lose too much muscle and it makes it easier to maintain your weight over the long run. Losing more than 3 lbs a week can be bad if you aren't up on nutrition, not to mentention how bad it can be if you are a competitive rider.

Best of luck to you!!