Practice your eating plan the day before the long runs. After 5 or 6 pre-race eating days, you should have a plan that works for you. Avoid eating a lot of food after about 2pm the day before. If you get hungry, eat a snack which can be digested easily, about every 2-3 hours. Since it takes about 36-48 hours for food to be digested, metabolized, etc., the food you eat the day before will not help you during the race—and too much of it can hurt you.