You need to start eating more. Our bodies were designed to survive famine, not built to burn fat – so you have to set up an environment where you body can burn fat for fuel.
Because you are doing alot of riding, you are burning way more calories than you are consuming and you are hording onto the fat you have. (to put it simply, your body thinks its starving so it slows down its metabolism)
Can you please direct me to the science behind this statement that when you are in caloric deficit you need to eat more to lose weight due to metabolism – Thanks.