It's a little astonishing to me that I did lose 30 pounds the first year I started bicycling, because long bike rides make me SO hungry, and I know that I eat a lot more after a bike ride than I burned. Part of it is "I just biked 50 miles I can eat anything I want" mentality, and probably some of it is my post-ride food choices that lead me to feeling hungrier.
I was a little overweight when I started biking and I got fairly fit. This year my commute is too short, and I've been really awful about eating terrible foods, and my pants are getting tight. However, I'm not (much) worried about weight for anything other than cosmetic reasons. I know that if I pack on pounds despite daily bike rides, I'm still maintaining some fitness, like my low resting heart rate, low cholesterol, low blood pressure. That's not to say I wouldn't be healthier if I weren't gaining weight, but I'd be a lot less healthy if I were gaining weight but not biking 3 miles and walking between buildings & up steps every day.
2009 Trek 7.2FX WSD, brooks Champion Flyer S, commuter bike