Originally Posted by Brian Stone
When preparing to run a half marathon recently, I came across a ton of advice of the usual kind - eat plenty of pasta / carb load 24-48 hours before. However, I wondered about this when I was thinking it over. My understanding is that the goal of eating plenty is to ensure that glycogen and sugar stores are all maximized so that I'm in a well-fed state and storing as much ready energy as possible going into the event.
With that in mind and assuming this is correct, shouldn't I be just as well off regardless of types of macros eaten provided that I eat plenty of food and get sufficient rest? I have no reason to avoid carbs and that isn't my intent, but at the same time it didn't seem to make sense to me to go out of my way to carb load provided I'd be otherwise inclined to eat plenty of food and get plenty of rest during this period.
The availability of carbohydrate determines how long an athlete is able to exercise at intensities >50-65% VO2 max so by carb loading to maximize glycogen stores instead of following your regular diet you can improve performance by delaying the onset of fatigue.
AIS Sport Nutrition Factsheet: Carbohydrate Loading.
Runner's World 60-Second Guide: Carb-Loading.