How Many Carbs Can You Really Handle? The Science Behind High-Carb Fue

How Many Carbs Can You Really Handle? The Science Behind High-Carb Fuelling For Endurance Athletes

Is the Secret to Ironman Success Eating 180g of Carbs an Hour? At the 2025 Ironman World Championships in Nice, Norwegian triathlete Casper Stornes shocked the endurance world by fuelling with 182g of carbs and nearly a litre of fluid per hour. His bold strategy has fuelled a heated debate: is ultra-high carb intake the next breakthrough in endurance performance, or simply a recipe for gut distress? Endurance athletes everywhere are now asking, how much carbohydrate can your body really handle, and should you be pushing past the 90g/hour limit?

Why are athletes chasing higher carbs?
Can your gut really handle over 90g of carbs per hour?
Do everyday athletes need this much?
How much fluid do you need with big carb intakes?
So, is high-carb fueling the future of endurance sport?
Takeaway

Why are Athletes Chasing Higher Carbs?

Tour de France riders like Tadej Pogačar, elite ultra-endurance runners and Norwegian triathletes are leading the high-carb movement, often called “the Norwegian Method,” which focuses on maximising hourly carb intake to maintain steady energy throughout races and training.
A higher carb strategy may help delay fatigue and gain a competitive edge (1,2).
Higher carb intake may support faster recovery between sessions.
Sports nutrition science shows gut adaptation can allow higher carb tolerance.

Can your Gut Really Handle Over 90g of Carbs Per Hour?

Anecdotally, many elite athletes tolerate >90g/hour with gut training using a glucose-to-fructose blend (2:1 or 1:0.8 above 60g/hour) which has been shown to enhance absorption and lower the risk of gut discomfort (1,3,4,7).
Athletes often use a mix of powders, gels and real foods to reach these targets, depending on preference and tolerance.
There is limited peer-reviewed research examining carbohydrate intakes exceeding 90g/hour during endurance events.
Most of the existing research on consuming over 90g of carbs per hour has focused primarily on men (3,4).

Do Everyday Athletes Need This Much?

For most athletes, consuming more than 90g of carbohydrates per hour hasn’t been shown to improve performance (4).
Absorbing more than 90g/hour does not necessarily boost endurance, even though it fuels working muscles (4,5).
For endurance events lasting over 2.5 hours, it’s recommended to consume up to 90g of carbs per hour (5,6,7,8).
Intakes above 90g/hour may benefit from a 1:0.8 glucose-to-fructose mix to enhance absorption and reduce gut discomfort (4,7).
In ultra-endurance events, intakes up to 120g/hour may help when glycogen is fully depleted (4,5), but higher intake does not spare glycogen.
Higher carbohydrate intake can also increase the risk of flavour fatigue.

How Much Fluid do you Need With Big Carb Intakes?

For endurance events, aim for 600-1000 mL of fluid per hour (8,9).
Fluid helps carry carbs through the gut, and higher amounts are needed with >90g/hour to reduce bloating and nausea (8,9).
Many elite athletes pair 800-1000 mL of fluid with >90g of carbs/hour (e.g. Casper Stornes used 939 mL/hour at Ironman Nice World Champs).

So, is High-Carb Fuelling the Future of Endurance Sport?

As high hourly carbohydrate intake gains attention in endurance sports and research continues to explore it, we may see new innovative fuelling recommendations emerge in the future.
Future fuelling strategies will likely focus on tailoring carbohydrate intake to each athlete’s gut tolerance, training status, and event demands, including more research on female athletes.

Takeaway

Up to 90g/hour is evidence-backed for most endurance events >2.5 hours.
>90g/hour may be possible with gut training and multiple transportable carbs.
Fluid intake of 600-1000 mL/hour helps reduce GI issues.
Individual tolerance varies, especially for female athletes.

Ash Miller
Dietitian and Nutritionist (Masters)
Bachelor of Physical and Health Education
Instagram: @ashthomo_nutrition

Disclaimer:

The content in this blog is for general information only and is not a substitute for professional medical advice, diagnosis, or treatment. Always speak with your doctor or allied health team before changing your diet, exercise, or taking supplements, especially if you have a health condition or take medication. Please use this information as a guide only. Aid Station doesn't take responsibility for individual outcomes.

References

Virbay, T., et al. (2020). Effects of 120 g/h of Carbohydrates Intake during a Mountain Marathon on Exercise Load and Exercise-Induced Muscle Damage Markers. Nutrients, 12(5), 1367.
Baur, D.A.; Saunders, M.J. Carbohydrate Supplementation: A Critical Review of Recent Innovations. Eur. J. Appl. Physiol. 2021, 121, 23–66.
Müller, M., et al. (2020). Effects of 120 g/h of Carbohydrates Intake during a Mountain Marathon. Nutrients, 12(5), 1367. https://doi.org/10.3390/nu12051367
Jeukendrup AE. The optimal carbohydrate intake during exercise. Sports Med. 2010;40(6):499–511.
Burke LM et al. Carbohydrates for training and competition. J Sports Sci. 2011;29(Suppl 1):S17–27.
Rollo I, Gonzalez JT, Fuchs CJ, van Loon LJ, Williams C. Carbohydrate supplementation and endurance performance: a systematic review. Sports Med. 2020;50(Suppl 1):3–23.
Podlogar T., Bokal Š., Cirnski S., & Wallis G. A. Increased exogenous but unaltered endogenous carbohydrate oxidation with combined fructose-maltodextrin ingested at 120 g h-1 versus 90 g h-1 at different ratios. Eur J Appl Physiol. 2022;122:2393–2401.
Sports Dietitians Australia. (2015). Fluids in sport. Sports Dietitians Australia. https://www.sportsdietitians.com.au/wp-content/uploads/2015/04/Fluids-in-sport.pdf
2. International Society of Sports Nutrition. (2010). Position stand: Exercise and fluid replacement. Journal of the International Society of Sports Nutrition, 7(1), 7. https://jissn.biomedcentral.com/articles/10.1186/1550-2783-7-7