I lost 35 pounds about a year ago, and for me its a combination of biking and the right diet. Not just calorie restriction, but I found out that I have impaired glucose tolerance so even with caloric restriction and tons of riding I couldn't lose. I also had to get my thyroid meds optimized.

For me what is key is that I eat a very low carb / high protein diet which lets me keep my blood sugar in a good range, which in turn lets me burn body fat for energy on the bike. So, be sure to get your doc invovled to find out if there are reasons you aren't losing weight if you think you are doing everything else right.

I also think a lot of cyclists, even with normal glucose tolerance, over eat carbs on the bike which inhibits fat burning. When carbs are high, the ratio of insulin to glucagon is high, which while good for letting the glucose get out of your blood and into your cells, inhibits fat burning. Instead I drink protein shakes on the bike, so I fuel my rides on a mixture of stored fat, and carbon skeletons from the amino acids (which are also slowly converted to glucose by gluconeogenesis). This isn't conventional advice, but it worked for me, and I have maintained my weight loss easily.