Why do so many people only run on water?
Do you think the training will have more effect? That it's not needed? I can perform anyway. Are you afraid of eating too many calories? I don't know the reason.
However, having cycled for many years (both road and mtb), I have noticed that many appear to be happy if they can ride on water alone.
I really want to bust this myth or ignorance - or whatever it is!
If you want to be able to push harder and improve your performance, you need the carbohydrates. If your session is longer than an hour, you need to add carbohydrates.
If you want to improve your performance, you need the carbohydrates!
If you don't have carbohydrates available when you exercise, you'll get tired faster, you won't be able to push hard (which slows down your progress), your recovery will be slower and your immune system will be weaker.
The only time you can benefit from cycling without carbohydrates (for more than an hour) is if you are doing a very low-intensity session where you want to increase your fat-burning capacity, read more about it here.
However, it shouldn't be done too often as it will put more strain on your body than it gives.