Published October 17, 2025 06:00AM

The Ironman World Championship has emerged as a significant platform for the “carbohydrate revolution”. This movement emphasizes the essential role carbohydrates (carbs) play in optimizing athletic performance. Athletes are continually exploring new avenues in sports nutrition, and the high-carb fueling strategies showcased during the Ironman World Championship races in Nice and Kona have illustrated the remarkable progress being made.

The Rise of High-Carbohydrate Fuels

For the past 15 to 20 years, the guidelines for fueling in endurance sports have transformed dramatically. Initially, recommendations suggested athletes consume roughly 60 grams of glucose per hour, a figure largely predicated upon limitations in intestinal absorption. However, advancements in research, particularly regarding the combination of glucose and fructose, have demonstrated that these mixtures can enhance carbohydrate absorption rates.

From 2010 to 2013, the recommendations evolved to suggest consumption levels of 60-90 grams per hour for events lasting longer than 2.5 hours. More recent studies indicate that elite athletes participating in events like the Giro d’Italia, Tour de France, and Ironman events perform best when consuming 90 to 120 grams per hour. This shift allows for better recovery and reduced muscle fatigue.

The pros competing this year at the Ironman World Championship have taken these findings to heart, with many athletes routinely consuming 120 grams or more per hour, pushing beyond what current research suggests.

Fueling Strategies from the Pros in Nice, France

Casper Stornes (NOR)

Performance Summary: Casper Stornes achieved a remarkable victory with a time of 7:51:39, including a groundbreaking run split of 2:29:25—the first sub-2:30 marathon in Ironman World Championship history.

Fueling Breakdown:

• Pre-Swim: ~60 grams of carbs
• T1: 80-100 grams
• Bike: 175-180 grams carbs, 720 calories/hour
• Run: 100-120 grams carbs, 400-480 calories/hour

In total, Stornes consumed approximately 182 grams of carbs per hour, which is a crucial aspect of maintaining high performance, confirming the effective training of his gut to handle substantial carbohydrate intake without any gastrointestinal distress.

Kristian Blummenfelt (NOR)

Performance Summary: Coming in third, Blummenfelt clocked in at 7:56:36, showcasing the fourth-fastest bike split at the event.

Fueling Breakdown:

• Bike: 177 grams carbs, ~710 calories/hour
• Run: ~130 grams carbs, ~520 calories/hour

Similar to Stornes, Blummenfelt’s fueling plan underscores the importance of meticulous preparation and testing to ensure optimal nutrient intake during the race.

Jamie Riddle (RSA)

Performance Summary: Riddle finished 10th with a time of 8:15:00 during his rookie Ironman.

Fueling Breakdown:

• Fueling Totals: 130 grams carbs, 520 calories, 878 mg sodium/hour

Riddle’s strategy, while less intensive than that of his competitors, still highlighted the crucial role that adequate fueling plays in achieving a competitive result in a major endurance event.

Fuelling Strategies from the Pros in Kona, Hawaii

Solveig Løvseth (NOR)

Performance Summary: Winning first place, Løvseth finished in 8:28:27 with a strong marathon split.

Fueling Breakdown:

• Pre-Race: Included multiple high-carb items such as gels and toast.
• Bike: ~145 grams carbs, 41 oz of fluid, and 1,103 mg sodium/hour
• Run: 139 grams carbs, 63 oz of fluid, and 1,536 mg sodium/hour

Løvseth’s approach illustrates how targeted training on gut tolerance can lead to successful fueling, especially in challenging conditions.

Kat Matthews (GBR)

Performance Summary: Matthews came in second with a time of 8:29:02, setting a new Kona run course record.

Fueling Breakdown:

• Breakfast: 150 grams carbs
• Run: ~60 grams carbs, 500-1000 mg sodium/hour

Matthews’ strategy demonstrates effective planning and adaptation to the rigors of race day, validating the significance of consistent training for gut tolerance.

Expert Analysis and Implications for Age-Group Athletes

Fueling strategies employed by elite athletes remind us that consuming 180 grams of carbs per hour is aggressive but essential for their specific demands. For age-group athletes, however, racing at lower intensities for extended durations requires a different approach. Attempting to mimic a pro’s fueling strategy can lead to adverse effects.

Most age-group athletes benefit from consuming 70-90 grams of carbs per hour, which is generally sufficient for optimal performance. Effective and practical fueling in endurance sports must match the individual’s training level, capacity, and environmental conditions.

The truth remains—training and racing are lifestyle activities for many individuals balancing private and professional responsibilities. Hence, meticulous metabolic testing and gut training may not always be feasible.

For age-group athletes struggling to maintain energy levels despite consuming ample carbs, metabolic testing may help to refine their fueling strategy. The right approach is to practice fueling at race intensity during training to ensure familiarity, which can lead to better results on race day.

In sum, the carbohydrate fueling strategies employed by professional triathletes this year in Nice and Kona highlight a significant method to enhance performance. However, these high-carb plans may not suit every athlete, especially when considering the unique needs of age-group competitors. Individualized fueling plans crafted from extensive training and testing can yield the best race results, regardless of one’s competitive level.