While you might think that, I have not had that experience, nor have I seen it when reading journals from people spending that kind of time in the saddle (try reading crazyguyonabike.com to see what I'm talking about).

Carbing up will be detrimental (no news there) but your body will still demand that you either consume enough calories to keep you going, or slow down. I bonked one day last summer on my Blue Ridge Parkway ride because I didn't get enough rest and used up all of my glycogen. I had to pull over and chow down on some macadamias and rest for about an hour. it got me going, but taught me a lesson on fuel vs. expenditure.

Goog