Biking is good for cardiovascular workouts and burning calories, but you will have to simultaneously control calorie intake if you want to lose any weight. The problem, especially as we grow older, is doing this while preserving muscle mass, so a variety of complementary workouts will help more. If you can do 100 miles/week and not change your calorie intake, you can start to slowly drop a few pounds per month. If you can sustain that while significantly cutting intake, especially simple sugars, then you can probably drop a lot more.