The figure's roughly 3500 calories per pound. If you can be on a deficit of 500 calories a day plus ride a little more on weekends, you can easily lose 2-3 pounds a week. It'll take about a month, a little less if you really get into cycling. Try jogging a little too, to add some variety. I lost 7 pounds in about a month without even realizing it after I got my road bike and all I did was bike 2-3 hours every morning on weekends and all that time I was eating MORE than what I had been eating before.
Just get out and bike!
