Sweating is pretty much irrelevant except as an indicator of effort--it's just water, and it comes back as soon as you rehydrate. Power Bars and Gatorade are often the culprits in things like this. A friend of mine used to whine about not losing weight, and when he tracked his intake carefully, he was doing almost 4000 calories a week in "sports drinks" and "energy bars" IN ADDITION to regular meals. He'd pound a Power Bar and a bottle of Gatorade for a half-hour ride that probably used 250 calories. Weight's not coming off that way.