I have been following a LCHF diet for about 3 weeks now. Works really good for now but I never went for a ride on the bike yet. I do however run 30 minute sessions 3 times a week. Never felt the lack of energy.
http://www.youtube.com/movie?v=evcNPfZlrZs
I advice anyone who wants to learn about low carb to watch this documentary. Even if you're not a low-carber, take a look.