Breaking Change in the Science of Ultramarathon Fueling
If you've been following ultramarathon nutrition guidelines from just a few years ago, prepare to throw out the playbook. Recent research from elite competitions, including groundbreaking studies from the 24-h World Championships and the 2022 Seville Marathon are revealing that top performers are consuming far more carbohydrates than previously thought possible, with stunning results.
The paradigm shift? Elite ultramarathon runners are now successfully consuming 60-120 grams of carbohydrates per hour during races, significantly exceeding the traditional 30-60g recommendations that dominated sports nutrition for decades.
What the Latest Research Shows
Elite Performance Data from the 24-Hour World Championships
A landmark study analyzing 12 elite French national team members during the 24-hour ultramarathon World Championships revealed eye-opening findings. According to the research published in the Journal of the International Society of Sports Nutrition, these world-class athletes consumed an average of 1,490g of carbohydrates over 24 hours, translating to approximately 62g per hour for those running between 193-272 km.
Most remarkably, 11 of the 12 finishers exceeded minimum nutritional recommendations, with energy intake positively correlating with race performance. The athletes maintained this unprecedented intake without significant gastrointestinal distress or exercise-associated hyponatremia, two concerns that have historically limited carbohydrate consumption during ultra-endurance events.
Marathon Runners and the 60-90g Sweet Spot
Complementary research from the 2022 Seville Marathon study found that runners who met carbohydrate intake recommendations of 60-90g per hour during competition were significantly more likely to finish in under 180 minutes. However, the study also revealed a concerning gap: most marathon runners consumed only 35 ± 17g/h, well below current recommendations.
The Science Behind High-Carb Fueling
Breaking Through the Oxidation Ceiling
For years, scientists believed that the human body could only oxidize about 60g of carbohydrates per hour during exercise, limited by glucose transporter capacity in the intestinal wall. Recent research has changed this assumption.
Studies now show that by consuming multiple transportable carbohydrates, combining glucose sources with fructose at approximately a 2:1 ratio, athletes can achieve oxidation rates of 90g per hour or higher.
According to the International Society of Sports Nutrition Position Stand on ultra-marathon nutrition, current recommendations now suggest 30-50g of carbohydrates per hour for ultra-marathons, with the acknowledgment that trained athletes may benefit from higher intakes approaching 60-90g per hour.
Gut Training: The Missing Piece
The key to tolerating these unprecedented carbohydrate loads? Progressive gut training. Recent guidelines from the Turkish Journal of Sports Medicine emphasize that athletes must systematically train their gastrointestinal systems to handle high-carbohydrate intake, just as they train their cardiovascular and muscular systems.
This involves gradually increasing carbohydrate intake during training sessions, allowing the gut to adapt by upregulating glucose transporters and improving gastric emptying rates.
Practical Implementation Strategies
Training Phase: Building Your Carb Foundation
During preparation, the research suggests ultra-marathon runners should target 5-8g of carbohydrates per kilogram of body weight daily. For a 70kg runner, this translates to 350-560g of daily carbs, significantly higher than general population recommendations.
The latest nutritional strategies review recommends:
- Short training sessions (<1 hour): 5-7g/kg/day
- Moderate sessions (1-3 hours): 7-10g/kg/day
- Extreme training (>4-5 hours): 10-12g/kg/day
Race Day: The High-Performance Protocol
For race day, elite protocols now recommend:
- Pre-race (1-4 hours before): 1-4g/kg of body weight
- During races <81km: 30-50g carbs per hour
- During races >81km: 60-90g carbs per hour
- Elite athletes in key race stages: Up to 120g carbs per hour
The 24-hour World Championship data showed successful athletes consumed 150-400 kcal per hour, with carbohydrates comprising the majority of this intake.
Carbohydrate Sources and Variety
To achieve these high intake rates, athletes should use multiple carbohydrate sources:
- Sports drinks: Providing 6-8% carbohydrate solutions
- Energy gels: Concentrated sources delivering 20-30g per serving
- Chews and bars: Providing texture variety and sustained release
- Real food: Increasingly important in ultra-marathons for palatability
Critically, combining glucose and fructose sources (approximately 2:1 ratio) maximizes absorption and oxidation rates by utilizing different intestinal transporters.
Addressing Gastrointestinal Concerns
One of the most significant findings from recent research is that trained athletes can consume these high carbohydrate loads without debilitating GI distress. In the 24-hour World Championship study, while 75% of athletes experienced some GI symptoms, these were transient (lasting only 3.0 ± 0.9 hours) and didn't significantly impair performance.
Strategies to minimize GI issues include:
- Progressive gut training during preparation phase
- Using multiple transportable carbohydrates (glucose + fructose)
- Avoiding high-FODMAP foods during racing
- Maintaining consistent consumption patterns
- Acquainting gut with all race nutrition during training
The Hydration and Electrolyte Connection
High carbohydrate intake must be balanced with appropriate fluid and electrolyte consumption. The latest research recommends:
- Fluid intake: 450-750 mL per hour (approximately 150-250 mL every 20 minutes)
- Sodium: 500-700 mg/L or 300-600 mg per hour
- Higher needs in hot conditions: Both fluid and electrolytes must increase
The Performance Impact
The relationship between carbohydrate intake and performance is now clearly established. The 24-hour World Championship research demonstrated a positive correlation between energy intake and distance covered. Athletes who met or exceeded carbohydrate recommendations consistently outperformed those who didn't.
Individual Variation and Personalization
While these recommendations provide evidence-based targets, the research consistently emphasizes individual variation. Factors affecting optimal carbohydrate intake include:
- Body weight and composition
- Running intensity and pace
- Environmental conditions (temperature, altitude, humidity)
- Individual GI tolerance and training status
- Race distance and duration
- Previous fueling experience
Practical Takeaways for Runners
Based on the latest research, here's your action plan:
- Increase daily carb intake during training: Target 5-8g/kg body weight, adjusted for training volume
- Start gut training now: Progressively increase carb intake during long training runs
- Test high-intake strategies: Work up to 60-90g per hour during key training sessions
- Use multiple carb sources: Combine glucose and fructose in approximately 2:1 ratio
- Don't neglect sodium: Ensure 500-700mg per liter of fluid, especially in heat
- Practice race nutrition consistency: Use identical products and timing in training
- Monitor and adjust: Track intake, GI symptoms, and performance to optimize your personal strategy
The Bottom Line
The ultramarathon nutrition landscape has fundamentally shifted in the past two years. Elite athletes are successfully consuming 60-120g of carbohydrates per hour, exceeding traditional guidelines with measurable performance improvements and manageable side effects.
This high-carb revolution isn't just for professionals. With proper gut training, appropriate product selection, and individualized planning, recreational ultra-runners can harness these strategies to improve performance and enjoyment of these incredible endurance challenges.
Want to implement these strategies? Start with your next long training run. Gradually increase your carbohydrate intake, monitor your body's response, and adjust accordingly. Remember: the gut is trainable, and the performance benefits are real.
