At the health and fitness expo held before my first marathon(The San Antonio Rock and Roll marathon), I was able to hear a nutrition presentation by Linda Farr, R.D.
The talk was titled Fueling Your Race:
Know what your goals are. Training is also to train your intestinal system.
On the day of the event, you should eat the same way you do during your training.
Look for foods that are low glycemic carbs and complex.
If you need a goal for protein, you should aim for 15% of protein(.5-.6g/p per day).
Make sure to stay hydrated.
During your taper, make sure to keep your diet the same. The day before the race, drink 4-8 extra glasses of water. You should start carb loading a couple of days before the race.
Ideally, these would be low fat, fruit, spaghetti, baked potatoes, cereal, energy bars.
You should try to avoid grapenuts, bran, pinto beans, fiber supplements, tacos, simple carbs/simple sugars.
It can take food a few days to go through your GI trac.
1-3 hours before the race, carb load and have energy bars on hand. Bring fluid with you(know where the water stations are). Have 2-3 glasses of water 2 hours before the race. Have one glass of water before the start of the race. Have an 8oz sports drink 15-20 minutes into the race. Have a snack every hour after 90 minutes of running.
Your first priority is hydration. The goal at the end of your workout should be the same weight as when you started. You can measure your sweat loss(1lb of weight loss = 3 cups of water)
What to look for in an energy drink:
Look at the percentage of carbs and sugar. 5-8% carbs, make sure it has sodium.
It can take several weeks for your muscles to rebuild.
Everyone has a different sweat rate.
Check out http://www.nutritioustable.com
Marathon Bars are a series of energy bars and protein bars.