Seriously, there's no magic 'thing' that's going to make you lose weight by doing it for 'X' number of hours.
Eat less, work out more. Period. As long as you do that you'll lose weight regardless of what work out you choose... go run, go climb a mountain, ride a bike... whatever. The truth is though, as soon as you stop and go back to your old ways the weight will come back. The only way you can actually change your weight is to change your lifestyle.
Currently, you eat 'X' amount of food and expend 'X' amount of calories throughout the day and your body has adapted to that. As soon as you start working out and losing weight, your body will then require less calories to maintain that new weight so you wont ever be able to again go back to eating the same thing you eat now... this simple principle is why 99% of diets fail. People stop the exercise and keep on eating what they've been eating and wonder why they're fat again.
So, put simply, if you want to continue to eat the way you currently eat then you will need to do some excercise, biking or whatever you chose, for the rest of your life in order to lose weight and keep it off... if you do it for 'X' number of hours, then you wont get any benefit from it really.
