At the risk of potentially sending some readers to the hospital with my hard core advice, I have found for me the best exercise to lose weight is high intensity training, not low intensity. FOR ME, exercising at a quick pace for short durations is more effective than long, slow workouts. If you are interested, check out HIIT (High Intensity Interval Training). My best workouts are less than an hour. Instead of plodding along for 2 hours on your bike, try hammering away for a full minute, then back off to an easy pace for 2-3 minutes....then repeat for 30 minutes. Hill repeats are good for this kind of workout. Find a good hill and climb it as fast as your can for a minute or two, then turn around and coast down. Catch your breath for a few moments and then repeat. Long, low intensity workouts do not work for me.
But all of this will not likely result in significant weight loss if you are not controlling your eating. There is an old bodybuilder's saying that "abs are made in the kitchen".