Tomorrow is the 31st annual Marine Corps Marathon. Racers are resting today, doing random things like picking up packets and making sure they have all their supplies organized. Many are getting ready for a big plate of pasta tonight. That's probably not the best idea.
From an evolutionary perspective, fat was the prefered endurance fuel. The sorts of carbohydrate-laden foods and drinks modern athletes consume did not exist; in fact, there were no simple carbs 100,000 years ago. Our ancestors ate wild plants that were very high in antioxidants and consumed as much fat as they could, meaning that the lean animals they ate had to be processed to capture all their fat content.
From Art De Vany. Art is an econ professor (emeritus) at UC Irvine (you can read more about him here.) He is well known for eating the caveman diet before it was chic. He also thinks marathons are very bad for you (here are his top 10 reasons not to run, as if you needed any convincing.)
The current emphasis on carb loading may just be the result of too much money flowing from sports drink manufacturers and others with vested interests. You should read his post if you are in the health training industry or if you are about to run in tomorrow's race. And the best of luck to you. I'll be asleep.