No, a sprinter will use, what, 12-1300watts, whereas a regular (pro) rider will for the most time ride at ~250watts. A body in ketosis may be able to convert fat to energy fast enough for 250watts, but is utter incapable of doing that for 1300watts, so you need sugar.
I know from my own kendo training, that I will start fading after 5 minutes, so at recent tournament, I supplemented with gummybears between each match, in order to make sure that I had enough energy.