Go on long difficult rides, and when you get home, just eat what you would have eaten normally had you not ridden. I know it's much easier said than done, but this way (as opposed to a fast) your body is still getting some nutrition, just not as much as it would like to have. This creates a caloric deficit, and you can't help but lose weight, it'll happen.
I find this technique works better during warm months, it seems like the body is much more willing to shed extra fat in hot weather, and plus you won't be walking around with cold hands (I hate fasting in the winter). I'm 57 and lost quite a bit of weight last summer doing this.