If you have a good diet, I don't know that it matters. IF you have had simple carbs, exercising right after minimizes the insulin response and will make you feel better. Insulin, among other things, is partly responsible for storing calories as fat. I used to get quite tired on some holidays, finally figured out it was too much dessert. Now if I eat too much I go for a fast walk or run and I am fine.
BTW, the blood, liver and muscles have about 2 hours worth of glycogen (sp?) available so you should be able to do about that before crashing.