Oh man, you have opened the door wide now. A lot depends on your metabolism and the diet you are used to. Many of the cycling books say carb load before a ride but if you take that literally you may end up packing on weight. You don't need to carb load for a 20 mile ride. I am on a lower carb program so I have a special oatmeal with 16 grams of Carbs, 11 grams of Protein and 2 grams of fat. If the ride is going to spirited or over 40 miles I will add a piece of fruit. But I do my best to get 5 grams of Fiber. I eat 1 to 2 hours before a ride, got that from Joe Friel's book cycling past 50. I also start hydrating before the ride with at least 16 ounces of water. But I have a coach and a doctor that made my diet for me. Yours might be different.