Caloric Needs for Ultra Runners: More Than Just a Race
The caloric intake for ultra runners is not a simple, static number. It is a highly dynamic and individualized strategy that must account for vast differences between training days, race days, and recovery periods. While a sedentary person might aim for around 2,000-2,500 calories, an ultra runner's needs can be more than double or triple that on heavy training days and even higher during competition. The key distinction is that while ultra runners burn a massive number of calories—often between 600 and 1,000 calories per hour while running—their bodies can only absorb and process a fraction of that during the actual event, creating a substantial and unavoidable calorie deficit. The art of ultra running nutrition lies in managing this deficit, rather than eliminating it entirely, by providing enough consistent fuel to prevent a catastrophic energy crash, also known as 'bonking'.
Fueling Strategies During the Race
During a race, the priority shifts from general energy balance to immediate, digestible fuel intake. The intensity of exercise and the stress on the digestive system make it challenging to process solid food efficiently. For this reason, a carefully planned intake schedule of simple, fast-digesting carbohydrates is paramount. Successful finishers consistently consume more calories per hour than those who fail to finish.
- Start early: Begin fueling about 45 minutes into the race and continue consistently every 30 minutes thereafter. Waiting until you feel hungry or fatigued is too late.
- Prioritize carbohydrates: The primary fuel source is carbohydrates, with recommendations ranging from 60 to 90 grams per hour for many endurance runners. Elite athletes, who have trained their gut, can push this even higher, sometimes ingesting 100-120g of carbs per hour by using a glucose-fructose mix.
- Diversify sources: While gels offer a quick, concentrated source of carbs, flavor fatigue is a common issue on long races. It is crucial to diversify your fuel sources with a mix of sweet and savory options. Salted pretzels, potatoes, rice bars, and homemade energy balls can prevent taste bud burnout and provide variety.
- Integrate protein and fat: After several hours, supplementing carbohydrates with small amounts of protein and fat can be beneficial. This helps slow digestion and provides a more sustained energy release. Good options include peanut butter, cheese, or protein-enhanced endurance bars.
- Listen to your gut: Pay close attention to how your stomach is responding. Gastrointestinal issues are a leading cause of DNF (Did Not Finish) in ultra races. Experiment with different foods and quantities during training to find what works best for your body under stress.
Macronutrient Breakdown During Training
During heavy training phases, the focus is on recovery and building overall energy stores. Macronutrient ratios differ significantly from race day strategies, emphasizing higher protein intake for muscle repair. The specific daily calorie count will fluctuate based on the volume and intensity of training. A 65 kg male runner, for example, might need around 2550 kcal for a one-hour run day but up to 5400 kcal on a three-hour intensive training day.
- Carbohydrates (5-8 g/kg/day): This is the foundation of an ultra runner's diet, essential for replenishing glycogen stores. A "food-first" approach using whole grains, starchy vegetables, and fruits is best.
- Protein (1.7-2.2 g/kg/day): High-volume training causes significant muscle damage, so adequate protein intake is crucial for repair and recovery. Distributing protein evenly throughout the day, such as 20g every three hours, is an effective strategy.
- Fat (1.0-1.5 g/kg/day): Healthy fats are vital for energy production, hormonal balance, and absorbing fat-soluble vitamins. Options include nuts, seeds, avocados, and oily fish.
The Inevitable Calorie Deficit
Even with the best fueling strategy, ultra runners operate in a caloric deficit during races. For a 24-hour race, the energy expended (13,000-17,750 kcal) often far outstrips the calories consumed (4,000-5,000 kcal), leading to a significant energy gap. This deficit is a major physiological stressor and highlights the importance of nutritional planning during all phases of training and recovery. The goal isn't to match calorie expenditure, which is impossible during the race itself, but to provide enough fuel to keep the body functioning and to minimize the impact of the deficit on performance. Successful long-distance runners use a combination of pre-race carbohydrate loading and consistent, small-intake feeding during the race to manage this reality effectively.
Hydration and Electrolytes
Adequate hydration and electrolyte balance are inseparable from caloric intake for ultra runners. Dehydration impairs digestion, exacerbates gastrointestinal distress, and hampers performance. Overhydration, especially without sufficient electrolytes, can lead to dangerous hyponatremia. The best strategy is to balance fluid and electrolyte intake based on individual sweat rates and race conditions, rather than relying solely on thirst. A common guideline is to consume 450-750 ml of fluid per hour, along with 500-1000 mg of sodium per liter, adjusting for heat and humidity.
Comparison of Ultra Runner Diets
| Aspect | Training Day | Race Day | Multi-Day Race (15+ days) |
|---|---|---|---|
| Total Calories (Approx.) | Varies greatly based on training load (e.g., 2,500-6,000+) | 150-400 kcal per hour (significant deficit) | High volume, aiming for 6,000-10,000 kcal/day |
| Primary Goal | Replenish glycogen, repair muscles, recover | Consistent, easy-to-digest fuel to manage deficit | Consistent, high-calorie intake to combat massive deficit |
| Carbohydrates | Moderate-to-high (5-8 g/kg/day) from whole foods | Primarily from gels, chews, drinks (60-90 g/h) | Mix of fast and slow carbs, including real foods |
| Protein | High (1.7-2.2 g/kg/day) for muscle repair | Small amounts (5-10 g/h) in later stages | Essential for muscle repair; high intake during breaks |
| Fats | Moderate, from healthy sources (nuts, seeds) | Minimal, but some fat can be useful for longer events | Higher percentage of calories from fat due to volume |
| Foods | Wide variety of whole foods, fruits, vegetables | Gels, chews, simple sandwiches, potatoes, salted items | Wide variety including hot foods at aid stations |
Conclusion
In conclusion, there is no single answer to how many calories do ultra runners eat a day. The number is highly dependent on the phase of the athlete's schedule, with a dramatic shift from high-volume, balanced nutrition during training to a targeted, digestible calorie strategy during a race. The reality of ultra running is an unavoidable calorie deficit on race day, but strategic, consistent intake of carbohydrates, protein, and fat, coupled with meticulous hydration and electrolyte management, allows runners to perform optimally. Testing different nutrition plans in training is paramount, as individual tolerance varies. By focusing on smart fueling and listening to their body's signals, ultra runners can effectively manage their energy stores and push their limits in the world's most demanding endurance races. For more detailed nutritional guidance, consider consulting with a sports dietitian.
