The Absolute Necessity of In-Race Fueling
Unlike shorter endurance events, where stored glycogen might be sufficient, ultramarathons require continuous and strategic fueling. Ultrarunners can burn up to 18,000 calories over a 24-hour race, making it impossible to replace all expended energy. The goal is not to match calories burned but to minimize the energy deficit and maintain stable blood sugar levels. Failure to fuel properly can lead to the dreaded "bonk," where performance catastrophically declines due to depleted glycogen stores. In fact, nutrition issues are cited in up to 40% of ultra marathon DNFs.
The Macronutrient Breakdown for Ultras
Carbohydrates, protein, and fat all play a role, but their importance shifts throughout a long race. Carbohydrates are the most critical, serving as the body’s primary energy source for high- and moderate-intensity efforts. Protein is needed for muscle repair, which is significantly higher in ultras compared to standard marathons. Finally, fat provides a long-term, energy-dense fuel source that becomes particularly valuable in races lasting over 10 hours and can help with palate fatigue.
Hourly Fueling Targets for Ultrarunners
Research provides solid guidelines for hourly intake, which must be practiced and refined in training to find your personal tolerance level.
- Carbohydrates: 60–90 grams per hour is a widely recommended target, providing 240–360 calories. Some elite runners, after significant gut training, can tolerate up to 120 grams per hour by using multiple-transportable carbohydrates, such as a 2:1 glucose-to-fructose ratio.
- Protein: Aim for 5–10 grams of protein per hour, which can reduce muscle breakdown and combat central fatigue during longer events.
- Fat: While not the primary focus, incorporating some fat (around 5–7 grams/hour in longer ultras) is beneficial for energy density and savory cravings.
The Spectrum of Ultra-Running Food
Ultramarathon fueling can be a mix of purpose-engineered nutrition products and real food. Early in a race, when intensity is higher, quick-digesting gels and chews are common. As the race progresses and taste fatigue sets in, runners often crave more substantial, savory foods.
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Engineered Fuels:
- Gels and Chews: Provide a concentrated, fast-acting source of carbohydrates. They are easy to carry and consume on the move but can lead to stomach upset if not taken with water.
- Sports Drinks: Combine hydration with carbohydrates and electrolytes, offering a convenient all-in-one fuel source. Brands like Tailwind and Maurten are popular for their dual-carb formulas.
- Energy Bars: Good for solid calories and a mix of carbs, protein, and fats. They are best consumed during lower-intensity sections to aid digestion.
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Real Food Options:
- Savory Snacks: Salted pretzels, potato chips, and pickles are popular choices to replenish sodium and combat sweet fatigue.
- Carb-Heavy Items: Small sandwiches (like PB&J), rice cakes, or boiled potatoes provide more complex carbs and a sense of satiety.
- Soup and Broth: Hot broth is a welcome sight at aid stations, providing warmth, sodium, and comfort, especially in cold weather or during overnight stages.
- Sweet Treats: Bananas, candy, and cookies offer a quick sugar boost and a morale lift.
Comparison of Fueling Strategies
| Fuel Type | Pros | Cons | Ideal Use | Notes |
|---|---|---|---|---|
| Energy Gels/Chews | Highly concentrated carbs, easy to carry, quick energy absorption. | Can cause GI distress if not taken with enough water, intense sweetness can cause taste fatigue. | Early race, high-intensity efforts, quick boosts. | Experiment with different brands and flavors in training. |
| Sports Drinks | Hydration + carbs + electrolytes, can be drunk steadily. | Taste fatigue can occur, can lead to overhydration if used improperly. | Steady state sections, all race long to manage hydration. | Pay attention to sodium levels and adjust as needed. |
| Solid "Real" Foods | Provides satiety and variety, good mix of macros (carbs, fat, protein), combats taste fatigue. | Harder to chew and digest at higher intensities. | Longer, slower sections of the race; later stages when appetite shifts. | Pre-test all foods during training to ensure tolerance. |
| Soup/Broth | Savory and warm, excellent for sodium replenishment, settles the stomach. | Not practical to carry, must rely on aid stations. | Late-race, overnight, and colder stages. | Can be a lifesaver for struggling runners. |
The Crucial Role of Gut Training
One of the most common nutrition mistakes is not training the gut. Just as you train your legs and lungs, you must train your digestive system to handle fuel during strenuous exercise. This means consuming race-day nutrition during your long training runs, starting 8–12 weeks before the race. You should also practice fueling even when you don't feel hungry, as this will be essential in the later stages of an ultra. Athletes with sensitive stomachs may need to explore options like low-FODMAP foods in training to minimize cramping and bloating. Consistent practice builds tolerance and reduces the risk of gut issues derailing your race.
Hydration and Electrolyte Management
While eating is crucial, proper hydration and electrolyte balance are equally important. Drinking to thirst is a valid general guideline, but ultrarunners need a more proactive strategy due to high sweat loss, especially in hot conditions. Aim for 400–800 ml of fluid per hour, with 500–1000 mg of sodium per liter, adjusting for conditions and individual sweat rates. Excessive plain water intake can lead to hyponatremia, a dangerous condition caused by low blood sodium levels. Electrolyte tabs, salt-fortified foods, and sports drinks are all ways to replenish sodium and other minerals lost through sweat. For more on optimizing your hydration, review strategies from experts like Precision Hydration.
Conclusion: Fueling is the Foundation of Ultra Success
Yes, people eat during ultra marathons—and doing so successfully is arguably the most vital skill for any ultrarunner. The human body is remarkably resilient, but without a constant stream of fuel, it will inevitably falter over extreme distances. Mastering the art of in-race fueling—by training your gut, understanding your macronutrient needs, and managing hydration—is a non-negotiable part of preparation. By treating nutrition with the same seriousness as physical training, you significantly increase your chances of a strong, healthy, and successful race.
