Here in BF we have a special forum for questions just like this called Training and Nutrition:
http://www.bikeforums.net/forumdisplay.php?f=148

Go there and do a search ... your questions have already been answered.

We also have a forum called the Long Distance forum. If you're talking about distances of a century or longer, that would be another place to ask the question.
http://www.bikeforums.net/forumdisplay.php?f=231