Personally I think cycling is overrated as a weight loss 'tool.' In my case, I went from 400 pounds to 275 before I learned to ride a bike. (In fact, learning to ride was a motivation for learning to ride, since I was unaware 400 pound guys could sit on a bike without breaking it.)

Once I began to learn to ride, I dropped from 275 to 242 over five months. However, that was with maintaining a very strict diet and continuing a lifting/hiking routine of exercise. As I tapered off the lifting and riding became my 'primary' exercise, my weight began to climb. The biggest reason is that cycling gives me an enormous appetite. I'm never as hungry as I am after riding, and I find it hard to keep my eating in check.