Your Hourly Caloric Target
For most ultra runners, the general recommendation is to consume between 200 and 400 calories per hour. However, this is not a one-size-fits-all number. Your ideal intake will depend on several factors, including body size, running intensity, and metabolic efficiency. Heavier runners and those moving at a faster pace will naturally have higher caloric needs.
The absorption capacity of your gut is the primary limiting factor. During high-intensity exercise, blood flow is diverted away from the digestive system to the working muscles, which can hinder digestion. Most people can only absorb about 60 grams of carbohydrates per hour, which equates to approximately 240 calories. Advanced gut-training techniques, which will be discussed later, can push this limit higher, with elite athletes sometimes consuming up to 90-120 grams of carbs (and thus more calories) per hour.
The Importance of Macronutrient Balance
While carbohydrates are king for immediate fuel, a balanced intake of all three macronutrients is important, especially for longer races. Over time, relying solely on sugary gels can lead to palate fatigue and stomach issues.
- Carbohydrates: These are your body's primary and most efficient energy source. A mix of glucose and fructose (dual-fuel carbs) can help maximize absorption, as they use different intestinal transport pathways. Most athletes should aim for 60-90 grams of carbs per hour for events over 2.5 hours.
- Protein: A small, consistent intake of 5–10 grams of protein per hour during long events (over 12 hours) can help preserve lean muscle mass and reduce fatigue. Savory options like jerky or nut butters can help satisfy cravings for something other than sugar.
- Fat: While not a primary fuel source during high-intensity running, fat is energy-dense and can become more tolerable during very long events (12+ hours) or multi-day efforts. Including some fatty foods, like nuts or cheese, can add variety and energy density to your fueling plan.
Practical Fueling Strategies
Developing a race-day strategy is critical. You must practice your fueling plan extensively during training to train your gut to tolerate the stress of exercising and eating simultaneously.
List of Common Ultra Running Fuels
- Engineered Options: Gels, chews, and sports drinks are highly portable and provide easy-to-digest carbohydrates. Check the nutritional information to calculate your hourly intake.
- Real Foods: Variety is key to avoiding flavor fatigue. Options include small portions of peanut butter and jelly sandwiches, boiled and salted potatoes, pretzels, or rice balls.
- Liquid Calories: Sports drink mixes are an excellent way to get both calories and electrolytes simultaneously. Broth or soups (at aid stations) can also provide warmth and sodium later in a race.
Comparison of Fueling Approaches
| Fuel Type | Carbohydrate Source | Calorie Density | Pros | Cons |
|---|---|---|---|---|
| Energy Gels | Simple Sugars (Glucose/Fructose) | High | Fast-absorbing, convenient, easy to carry. | Can lead to flavor fatigue, stomach issues if not paired with water. |
| Sports Drink | Simple Sugars + Electrolytes | Low to Moderate | Hydrates and fuels simultaneously, good for consistent intake. | Can cause bloating if too concentrated or consumed too quickly. |
| Solid Food (e.g., PB&J) | Complex/Simple Carbs, Protein, Fat | Variable | Provides more complete nutrition, reduces sweet fatigue. | Slower digestion, can be hard to chew while running. |
| Salty Snacks (e.g., Pretzels) | Simple Carbs + Sodium | Moderate | Replenishes sodium, helps with sweet fatigue. | Low in overall calories, can be drying. |
Gut Training for Success
Your gut is trainable, just like your muscles. Consistently practicing your fueling plan during long training runs will help your digestive system adapt and become more efficient at processing food while running. Starting with a lower intake and gradually increasing it over several weeks or months is a safe and effective method. For instance, begin by aiming for 30-40g of carbs per hour and, after your gut adapts, increase to 60g or more if you can tolerate it without GI distress.
Conclusion: Practice and Personalize
Ultimately, there is no single answer to the question, how many calories should I eat during ultra running? The general guideline of 200-400 calories per hour provides a solid starting point, but personalization and practice are paramount. An ultra race is as much an 'eating contest' as it is a running race, and your ability to consume and tolerate consistent fuel is a primary predictor of success. By training your gut and experimenting with different macronutrient sources, you can develop a robust nutrition plan that prevents GI issues and powers you to the finish line. As you gain experience, your body will give you better feedback on what works and what doesn't. Listen to its cues and stay adaptable on race day. For further reading, an excellent overview of the science behind ultramarathon fueling can be found in the International Journal of Sport Nutrition and Exercise Metabolism.
What are some good, easy-to-digest real foods for an ultra run?
Some good options include boiled and salted potatoes, pretzels, rice balls, and small pieces of peanut butter and jelly sandwiches. These offer a mix of carbohydrates, salts, and sometimes a bit of protein, helping to combat palate fatigue from overly sweet products.
Should I eat protein during an ultra running event?
Yes, for events over 12 hours, consuming 5–10 grams of protein per hour can be beneficial. It helps reduce muscle breakdown and may contribute to satiety and mental focus. Look for options like jerky, nut butters, or recovery-style sports drinks.
What is gut training and why is it important for ultra runners?
Gut training is the practice of consistently eating and drinking your planned race-day nutrition during long training runs. It helps your digestive system adapt to processing fuel under the stress of exercise, reducing the risk of gastrointestinal issues like nausea, bloating, and diarrhea on race day.
How can I prevent stomach issues during an ultra run?
To prevent stomach issues, start fueling early in your race and eat small amounts frequently. Avoid large, heavy meals right before or during your run. Practice your nutrition plan extensively in training, stay hydrated with electrolytes, and listen to your body's tolerance for different types and amounts of food.
How does gender affect caloric needs for ultra running?
Recent research indicates some metabolic differences between men and women in endurance events. Women, for example, tend to oxidize more fat and may need to start with a slightly lower carbohydrate intake (around 30-40g/hr) during gut training, gradually increasing to 50-60g/hr. Fluid needs may also differ due to size and sweat rate.
What is the maximum amount of carbohydrates my gut can absorb per hour?
While the historical limit was believed to be around 60g/hr, modern research and practice show that with dual-fuel carbohydrates (glucose + fructose), many athletes can train their gut to absorb up to 90-120g/hr, especially in controlled conditions. However, this requires specific gut training and is not suitable for everyone.
Do I need to use only sports nutrition products for an ultra?
No, it is not necessary to use only engineered sports products. In fact, many successful ultra runners incorporate real foods into their fueling plans to prevent palate fatigue and provide a wider variety of nutrients. Real foods like boiled potatoes, bananas, and sandwiches are common sights at aid stations and on the trail.
