I started a thread about this very subject.
I think for *some* folks, riding a LOT could cause weight gain. It ramps up your metabolism, which makes you hungrier, and then you eat more, and then it's harder to deficit.
The big event I train for is the first week in June. (Just completed it.) Training usually starts in January. I got a fancy Withings scale and planned to be very smart during training and the weight would just melt off. Yeah, that didn't happen. I've stayed within the same 5 pound range all year so far. The riding has gone up. My calves are huge. My quads poke through the fat. However my waist is the same and my weight is the same. At least I haven't regained a bunch.
I don't want to lose weight just to lose weight. I want to lose weight because I want to go faster and I think it's more efficient to drop weight rather than get stronger. If I can figure out how to keep the muscle I've gained while just dropping fat I bet I'd get much faster. I'm already faster than I was last year and about 15lb heavier, so I know I'm stronger. However the weight I've lost so far was done with a very moderate level of exercise and a pretty extreme calorie budget. I still haven't figured out how to ride the amount I want to ride and eat the right amount to lose weight at that level.