I personally have never been able to use diet to maintain my weight. Which is why a year of little exercise really did me in.
I just bought my road bike in January. I have no idea what I weighed at the time, but I was a size 14. Last weekend I bought the exact same jeans I have been wearing forever and they were a size 8. The only change in my life is that I ride my bike to work every day and to run errands. I usually do one ride of about 40 miles on the weekend.
In the last few months I have gone through times when I thought I could eat a house! Friends thought I was pregnant (I even started to wonder, despite no other signs). Anyway...I think it is a matter of keeping with it and not being too terribly hard on yourself. Also...toss the scale!