Fuelled or Fooled? Examining the Evidence and Mechanisms Behind Ultra-high Carbohydrate Intake in Endurance Athletes
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Plews, DJ
Booth, PD
Krieger, T
Maunder, E
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Springer Science and Business Media LLC
Abstract
Ultra-high carbohydrate (U-HC) ingestion strategies, typically > 90 g·h⁻¹, have gained remarkable traction among elite endurance athletes in recent years. This rise has been fuelled by anecdotal reports linking aggressive carbohydrate fuelling with superior race execution, and record-breaking performances. However, the scientific literature supporting these practices remains limited, and current frameworks used to explain carbohydrate-mediated performance effects, such as muscle glycogen sparing, maintenance of blood glucose or maximisation of exogenous carbohydrate oxidation, do not fully account for the reported U-HC benefits. Indeed, available studies reveal a disconnect between metabolic data and the real-world adoption of intakes far beyond established oxidation ceilings. We examine the existing research on carbohydrate ingestion during endurance exercise, highlighting the metabolic responses and performance outcomes. We identify how traditional mechanisms have been interpreted to justify escalating carbohydrate intake and discuss the constraints of current methodologies in detecting meaningful performance benefits at ultra-high ingestion rates. The article then introduces emerging, yet largely untested, possible mechanistic models that may underpin the perceived utility of U-HC fuelling, including shifts in substrate selection, enhanced lactate shuttling and potential central effects associated with carbohydrate availability. Finally, we explore the relevance of inter-individual variation in carbohydrate oxidation capacity and the implications for developing practical guidelines for athletes. By integrating physiological, metabolic and perceptual perspectives, this current opinion outlines why U-HC strategies have gained prominence and identifies key areas where further research is required to clarify their role within contemporary endurance performance for the masses.
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42 Health Sciences, 4207 Sports Science and Exercise, Clinical Research, Nutrition, 0913 Mechanical Engineering, 1106 Human Movement and Sports Sciences, 1302 Curriculum and Pedagogy, Sport Sciences, 4201 Allied health and rehabilitation science, 4207 Sports science and exercise
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Sports Medicine, ISSN: 0112-1642 (Print); 1179-2035 (Online), Springer Science and Business Media LLC, 1-22. doi: 10.1007/s40279-026-02462-z
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Open Access. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
