The night before the 1982 Beijing Marathon, running legend Bill Rodgers was invited by the race organizers to a lavish Chinese buffet. As a veteran of international events, the four-time winner of the Boston and New York City marathons was accustomed to pre-race meals besides the traditional pasta dinner. Still, he probably wasn't expecting the delicacy that was presented to him as the guest of honor: a 100-year-old bird egg that had been soaked in pig urine. "It didn't taste bad," Rodgers politely offers, but you sense he wouldn't have minded a lowly bowl of rice instead.

"The marathon is all about energy management," says Keith Brantly, who ran the event at the 1996 Olympics. In other words, it doesn't matter how well you have trained or how motivated you are if you run out of gas en route. Good nutrition is more important for the marathon than for any other popular distance. It's common sense on the morning of a 5K race not to fry up some eggs (or to soak them in pig urine, for that matter). But if you do, it's not as if you're going to crash and burn at the three-kilometer mark; you're just going to have an unpleasant gastrointestinal experience.

Because the marathon is so long, however, it almost never allows for such mistakes. Even the best marathoners in the world worry that their muscles will run too low on fuel to keep their pace until the finish. That's why "carbo-loading" is as integral to marathon lingo as "long run." It's also why, except when he had no choice in the matter, Rodgers's pre-marathon meals were more akin to dining scenes from "The Godfather" than the egg-eating contest in "Cool Hand Luke."

CARB CONUNDRUM

Better fuel means better mileage.

A little physiology explains why. The two primary fuels your muscles use while running a marathon are carbohydrate and fat. Carbohydrate is stored in the body as glycogen; fat is stored in the body as, well, look around. When you run, your body burns a mixture of carbohydrate and fat. The harder you run, the more carbohydrate you use; the slower you run, the more fat you use. The winners of Sunday's marathon will derive between 80 percent and 90 percent of their energy from carbohydrate, most of it coming from their muscles' glycogen stores.

As the miles continue and your glycogen stores become progressively depleted, your body tries to conserve what's left by burning more fat. Sounds great, huh? Not quite.

"The breakdown of fat requires more oxygen per calorie released than does carbohydrate, meaning that fat is a less efficient energy source," explains Pete Pfitzinger, a two-time Olympic marathoner and manager and lab director of the Sport and Exercise Science Department at the University of Auckland, in New Zealand. In other words, when you have to burn more fat, you slow as your body puts more energy into burning fat and less into powering your muscles, and you crash headlong into the infamous Wall.

Usually, the invisible but all-too-real Wall is said to stand at about the 20-mile mark of the marathon. The long runs that are the backbone of all marathoners' programs make muscles more efficient at storing glycogen and train them to conserve glycogen at a given pace. Even with these adaptations, though, most people eating a normal diet can store no more than 2,000 calories of glycogen in their muscles. A mile of running burns roughly 100 calories. A marathon is 26.2 miles. You do the math.

Enter what for some people seems to be the whole point of becoming a marathoner: carbo-loading. If you run, at most, a few miles a day in the few days before the marathon, and eat a high-carbohydrate diet, getting 70 percent to 80 percent of calories from carbohydrates during that time, then endurance-trained muscles can stash away as much as another 800 calories, and the Wall can get pushed beyond the finish line.

So, days of almost no running and endless plates of pasta? No one ever promised the marathon didn't require sacrifices. The thing is, most marathoners get carbo-loading wrong, although it's certainly not for lack of trying. The point is to increase the percentage of your calories that come from carbohydrates. This is different than following Olympic marathoner Don Kardong's tongue-in-cheek advice, "If you eat foods that are half as nutritious as they should be, eat twice as much."

Nancy Clark, author of "Nancy Clark's Sports Nutrition Guidebook," counsels, "Because you will be exercising less during the pre-event taper, you do not need to eat hundreds of additional calories when carbo-loading. Simply maintain your standard intake."

As for the makeup of that intake, it's important to be honest about what you're eating. Pasta with a light marinara sauce is a high-carbohydrate meal; fettuccine alfredo and similar artery-cloggers are not.

RACE DAY RATIONS

Don't blow it.

If you have carbo-loaded correctly, it is likely that you'll wake on marathon morning feeling bloated. (Of course, you probably will if you have followed the Kardong plan, too.) Explains Pfitzinger: "You should expect to gain a couple of pounds when you carbo-load, because your body stores 2.6 grams of water for every gram of glycogen. Don't be alarmed by the added weight. It's inevitable, and the stored water will prevent dehydration during the race."

Sorry, but carbo-loading doesn't mean a final bowl of risotto soon before the start. Your muscles' glycogen stores will be determined by how intelligently you approached the last few days' meals and mileage. On race morning, a light, high-carbohydrate breakfast -- 300 to 500 calories, such as a bagel with jam and a banana -- a few hours before the start will help to restore your liver's glycogen level, which helps to maintain your blood glucose level. If you have experimented with taking in carbs on the run in training, then you can continue to stave off glycogen depletion with smart nutrition during the marathon. If you haven't tried such treats as energy gels before, then skip the free gels that will be distributed at the 17.5-mile mark Sunday. As Clark puts it, "Don't blow it all by eating unfamiliar foods that upset your system." After all, marathon marvel that he was, the record shows that Bill Rodgers failed to finish his race the day after his Chinese delicacy.

Scott Douglas is a contributing editor for Running Times magazine and co-author of "Road Racing for Serious Runners."

Eating and Drinking on the Run

Between carbo-loading and post-race spreads lies the marathon. But nobody said the feast can't go mobile. A look at the most common things taken in during marathons:

Energy gels

Advantages

Gels supply about 100 calories -- roughly the amount burned in a mile of running -- of readily available glucose, the sugar that muscles prefer to use while running. This saves the body from using glycogen stores and extends the distance you can run. Pudding-like gels are easy to ingest while running.

Drawbacks

Can be a pain to open and carry while running. Many slower marathoners don't mind running with fanny packs or other means of toting gels, but many faster runners don't like the feeling of being weighed down.

Energy bars

Advantages

As with gels, bars supply calories that muscles can easily use, and they have a more satisfying texture. (Most contain about 200 calories.)

Drawbacks

Nearly impossible to chew without disrupting running rhythm. Carrying them requires fanny pack or other contraption.

Oranges

Advantages

Taste great, less filling. Easy to eat and give nice feeling of eating real food.

Drawbacks

An orange slice doesn't supply great amounts of water or energy. More important, the sugar in oranges, fructose, has to be converted to glucose before your muscles can use it, doubling the time it takes before the sugar reaches the muscles.

Sports drinks

Advantages

When properly mixed, sports drinks can rehydrate you as quickly as water, and they can supply needed energy. For example, 16 ounces of store-bought Gatorade contains 100 calories.

Drawbacks

If the drink isn't mixed with enough water, the sugar will sit in your stomach rather than quickly reach your muscles, and the fluid won't rehydrate you as quickly as water. Can also cause stomach problems, especially if you haven't tried the drink in training. (Marine Corps is using wild-berry flavored Ultima Replenisher.)

Water

Advantages

Duh. All the calories in the world won't help you if you become dehydrated, which can occur easily in a marathon even on a cool day. Performance starts to suffer after losing as little as 2 percent of body weight.

Drawbacks

None, really, as long as you don't ignore taking in calories as well.

-- Scott Douglas