With biking you dont burn that many calories. It would be better to go out and walk for the same amountof time and you could do nearley twice the work. I suggest since I'm a rower to try a rowing machine it burns calories like crazy. Yet, for you I would suggest running over biking its a lot harder a better workout and you can lose weight faster. One more suggestion mix it up you dont have to do the same workout everyday. Bike one day and run the next,