"Ultra races are more like eating and drinking contests. If you eat and drink enough, hopefully you will survive."
The above advice, given to me by a wise ultrarunning veteran, has been one of the most important keys to finishing my races. One simply has to eat and drink. And often!
Hitting "the wall" or "bonking," a phenomenon already well known to the marathoning community as being the point where ones body runs out of fuel and begins to shut down, could be catastrophic in an ultramarathon, where the distances covered are typically double and quadruple the standard 26.2 miles. Therefore, it is essential to eat and drink from the very beginning of the race.
Most people will require between 250-400 calories per hour, and it would be wise to include protein in any ultramarathon nutrition plan. The body is constantly being broken down. Protein will help it recover, slowly, as the race goes on.
Unlike the standard marathon aid station fare of strictly water and sports drink, an aid station at an ultramarathon will often look like a smorgasbord of high calorie junk food. The better races will also have a wide variety of "real" food. Peanut butter and jelly, eggs, grilled cheese and hot soups are commonly offered. If you're going to be out there running for 10 hours or more, you are probably going to want something more substantial than just gels.
Of course, we are all an experiment of one. I was on the support crew for a runner who ran 162 miles across the state of Illinois, and for 50-plus hours, all he really ate were gels and orange slices and he seemed to do just fine, successfully completing a run that many would consider slightly insane.
During my first 50-mile race, I too ate only gels and orange slices, which led to a bout of extreme nausea. Since then, I have practiced, with great success, the "see food" diet at ultras: I get to an aid station, take a look around, and whatever appeals to me at that particular time is what I eat. Sometimes it's potato chips, sometimes it's peanut butter and jelly, sometimes it's a burrito. I never know until I get there.
As much as possible, I do try to avoid foods with high sugar content, because excess sugar makes me feel queasy. But I know plenty of ultrarunners who do just fine on M&Ms and Mountain Dew.
The key is to practice. Find out what works for you. Experiment in training.
And always drink plenty of water.
The good news for runners is that now many ultra races use their aid station fare as key selling points to participate. The Potowatomi Trail Races are famous for their meatball sandwiches. The Evergreen Lake Ultra Series features skilled chefs whipping up batches of bacon and eggs. The Kettle Moraine 100 is known for its early morning treat of fluffy pancakes, a major pick-me-up for a tired, delirious runner.
So if you are going be running all day and possibly all night, you should not do it on an empty stomach. Get an early lead in the eating and drinking contest and your legs will do the rest.