I've sort of had the same problem for the past year or so. I'm your age and started riding last year due to bad knees and back and quite a bit of weight gain. Started at 238 lbs and am now sitting right at 170 with probably another 10 lbs or so to go. Most of last year my diet was 1 cup of lowfat yogurt with a sliced up banana and 1/4 fiber one for breakfast, banana or apple snack, Progresso light soup for lunch, another apple or banana snack, and then a sensible dinner. No eating after dinner unless a piece of fruit. I rode 20 miles 6 days a week drinking only water. After about 6 months I started some longer weekend rides and added a bit of carbs to my diet before the long rides.

Now that I am close to my goals I am still eating pretty much the same diet as above but eat more on the longer rides. My weekday rides are now in the 20 - 30 mile range and weekend rides are from 50 to 75 miles with longer rides every now and then. I'm also working on climbing and usually see two days a week climbing at least 9 miles at around an 8% grade. On these long days with lots of climbing I'm burning a couple of thousand calories easily and basically eat what I want yet the pounds keep coming off.

So, I guess my point is keep faithful to your riding, eat a sensible diet, and the pounds will come off. If you get your nutrition right on the rides you will meet your ride needs yet still be able to lose weight at a sensible rate.