The calf is thick not because there are many muscles, but because the subcutaneous fat is thick. See the figure below to compare the leg contours with the same muscle content and different fat content.
If you want to lose weight, you should do aerobic exercise. Riding is a good aerobic exercise.
When riding, it is best to let your heart rate reach 50%~75% of your maximum heart rate (220- age), and the effect of reducing fat is the best. Usually at this time, the speed of mountain bikes will be within the range of 20~25 kilometers per hour. Secondly, you'd better keep this speed and exercise 1 hour, and do this at least five times a week.
Pedal with the forefoot when riding.