I don't consider myself a high performance athlete. Since the OP is doing their first Century, I'm not sure they are ready to call themselves a high performance athelete.
Considering high performance athletes probably burn five to ten times, heck maybe even 20 times the Calories in a week that I do, then I don't think the things they are talking about translate well for us puny wannabe's. (if that's not you then disregard).