You need to understand first of all that you cannot say that you will lose weight just because you start cycling. Exercise can increase appetite greatly, and if you don't get the balance right there's every chance that you could maintain your weight, or even gain weight if your food intake increases dramatically. You also can't choose which parts of your body you lose weight from - there is no way to do this. However, biking is great for building leg strength, so increased muscle mass in this part of your body might make it look as though you have lost weight. It is certainly worth a try, and something that you should consider if you plan to cycle.