Ultramarathon Nutrition for Beginners: Eating Enough Without Destroying Your Stomach
Last Update January 27, 2026 by Etienne Durocher
Running 50 km, 100 km, or more isn’t just a test of legs—it’s a full-body endurance challenge. One of the biggest surprises for new ultramarathoners is nutrition. Many runners either underfuel or experiment too much during the race, leading to bonks, stomach distress, or premature fatigue.
Ultramarathon nutrition is about balance, planning, and gut training. The goal is simple: provide steady energy without creating digestive chaos. Done right, it allows you to focus on the trail, the rhythm of your stride, and the enjoyment of the adventure.
This guide walks you through the basics of fueling for ultra distances, with tips to prevent common mistakes that ruin even the most prepared runners’ day.
What You Need to Know First
Ultramarathon distances push your digestive system in ways shorter races do not. Even slight mismanagement of food, fluids, or electrolytes can lead to gastrointestinal distress.
Three core principles:
Calories matter: You burn significantly more than in a marathon, so fuel accordingly.
Gut adaptation is essential: Train your body to absorb calories while moving.
Plan, don’t experiment: Race day is not the time for new foods, gels, or supplements.
Remember, ultramarathon nutrition is a skill that develops gradually through long runs and multi-hour training sessions.
Building a Beginner-Friendly Ultramarathon Nutrition Plan
1. Calculate Your Fuel Needs
While individual needs vary, most ultramarathoners aim for 200–300 calories per hour during the race, sometimes more for higher intensity sections. Carbohydrates are the primary source, with small amounts of protein and fat if tolerated.
Tip: Start on the lower end in your first ultramarathon and adjust in training long runs. Listen to your energy levels and stomach comfort rather than rigid formulas.
Internal Link: Marathon Nutrition: Fueling Your Marathon – Practical Nutrition Strategies – the principles carry over, but volume and duration are much higher for ultras.
2. Training Your Gut
Your digestive system is your performance engine. Train it to handle fuel while moving:
Eat small portions of solid foods during long runs.
Experiment with gels, chews, or drinkable calories to see what your stomach tolerates.
Include fluids alongside calories to prevent dehydration and aid absorption.
Repeated practice reduces risk of cramps, nausea, and bonking on race day.
3. Hydration and Electrolytes
Ultra distances increase sweat loss and electrolyte depletion. Overhydration without electrolytes can be as dangerous as dehydration.
Guidelines for beginners:
Sip fluids regularly; don’t chase thirst.
Include sodium and potassium through sports drinks, gels, or salty snacks.
Monitor urine color and energy levels rather than blindly following a formula.
Internal Link: Trail Running Shoes Explained: Grip, Cushioning, and Protection for Long Distances – proper shoes help you stay efficient and avoid extra energy expenditure, supporting hydration and nutrition strategies.
4. Fuel Variety and Timing
Mono-fuel strategies rarely work for long ultras. A mix of gels, real food, and hydration keeps your palate engaged and energy steady:
Rotate sweet and savory options to avoid flavor fatigue.
Eat small portions every 20–30 minutes rather than large amounts infrequently.
Pair fuel with fluids for better absorption.
Long training runs are your test lab. Practice timing and portion sizes until your stomach and energy feel balanced.
5. Race Day Strategy
Beginner ultramarathoners often make two common mistakes: underfueling early and panic-fueling late. Avoid both:
Start consuming calories early and maintain a consistent intake.
Use familiar foods tested in training.
Adjust based on terrain and intensity: harder climbs may require slightly more energy, technical descents slightly less.
Internal Link: Trail Running Technique: How to Run Uphill, Downhill, and Technical Terrain Efficiently – terrain impacts energy demands and nutrition strategy.
6. Recovery Nutrition
Ultramarathon nutrition doesn’t end at the finish line. Recovery fuels muscle repair and glycogen replenishment:
Include carbohydrates and protein soon after finishing.
Rehydrate with electrolytes and fluids.
Light snacks in the following hours help stabilize blood sugar and restore energy levels.
Ultramarathon nutrition intersects with other aspects of performance. For a complete preparation approach, explore:
Trail Running Technique: How to Run Uphill, Downhill, and Technical Terrain Efficiently
Trail Running Shoes Explained: Grip, Cushioning, and Protection for Long Distances
Marathon Nutrition: Fueling Your Marathon – Practical Nutrition Strategies
Mastering these elements reduces digestive stress, prevents fatigue, and helps you enjoy every kilometer.
Practical Tips for Runners
Start fuel early, maintain consistent intake, and adjust to terrain.
Test every food and gel during long training runs.
Drink to thirst, supplement electrolytes, and avoid overhydration.
Rotate flavors to prevent taste fatigue.
Keep post-run recovery nutrition simple but effective.
Final Thoughts
Ultramarathon nutrition is as much about practice as planning. Your stomach, mind, and legs must adapt together. With the right strategy, energy intake feels automatic, digestion remains manageable, and you can focus on running efficiently.
Confidence in your fueling plan transforms ultras from unpredictable endurance tests into achievable, enjoyable adventures. Start small, experiment, and refine. By the time race day arrives, your gut, mind, and muscles will be prepared for the long haul.
What foods or gels have worked best for you during long training runs or ultras?
Have you noticed a difference when you fuel consistently versus reacting late?
For personalized guidance on ultramarathon nutrition, fueling strategies, and training integration, reach out or explore more resources on Philotimo Running Coach.
