Hi Donaldd,
Yes, welcome to the Forum! While you'll find an enthusiastic group of Thorn enthusiasts here who are always eager and willing to help, but you might find even more directed and helpful answers to your fitness and conditioning questions on a forum dedicated to that end. I'm thinking trainers, nutritionists, and sports kinesiologists could perhaps come up with a targeted conditioning program for you that would be a direct route to the contitioning and weight loss in the areas you seek.
That said, I have always been under the impression that except for muscle toning, conditioning, and strength, area-specific exercises don't do much to target fat in specific areas, like the belly or thighs. Those areas seem to store or lose fat as a consequence of overall fitness and body-mass index. If I were looking to reduce fat in specific areas, I think I would embark on a general conditioning program with lots of aerobic exercise in concert with a carefully tailored nutritional regimen, with diet being first on the list. As with any exercise or nutritional program, its always a good idea to consult your doctor first to make sure there are no underlying health conditons that might be a complication. Once you get the green light from your physician, you'll be in a much better spot to pursue exercise and nutrition.
And yes, bicycling either out in the world or on a trainer is a great way to increase overall fitnes and conditioning. It will improve muscle tone and strength. As for reducing fat in specific areas...not so likely. As a way to reduce overall body fat when coupled with diet? Yes, very effective, as is nearly any aerobic exercise. As Andy has said...do enough exercise, and you won't have to worry so much about diet, as you'll be burning off excess calories!
I hope this helps, and I wish you the best on your quest.
Dan.