Scientific Programme
Physiology & Nutrition
IS-PN02 - Contemporary Issues in Fuelling, Under-Fuelling and Re-Fuelling Male and Female Athletes: Revisiting Carbohydrate Guidelines for Athletes
Date: 07.07.2026, Time: 13:30 - 14:45, Session Room: Auditorium A (STCC)
Description
From a sport nutrition perspective, the primary need state for athletic populations is to ensure sufficient carbohydrate (CHO) before, during and after exercise. Nonetheless, despite over 100 years of research, considerable controversy exists on the optimal dose, blend and frequency of CHO intake that is required before, during and after exercise in order to promote training adaptations and performance. Indeed, whilst the r period of 2005-2020 was characterised by research recommending athletes practice carefully scheduled periods of “low CHO availability” in order to stimulate molecular pathways that regulate oxidative adaptations, the last 5 years have seen a marked rise in research in evaluating the pitfalls of such under-fuelling i.e. as related to relative energy deficiency in sport (REDS). Furthermore, anecdotal reports from endurance athletes are suggestive of fuelling above and beyond current sport nutrition recommendations (of 90 g.h-1) with intakes of 120-200 g.h-1 reported. In this regard, this presentation will review contemporary issues and recent research on fuelling, under-fuelling and re-fuelling. Data will be presented from the authors’ laboratories as will practical insights from their experiences of supporting some of the world’s best endurance athletes. This presentation will be highly relevant for sport scientists, practitioners, athletes and coaches.
Chair(s)
James Morton
Liverpool John Moores University, Research Institute for Sport and Exercise Sciences
United Kingdom
Speaker A
James Morton
Liverpool John Moores University, Research Institute for Sport and Exercise Sciences
United Kingdom
Read CVECSS Lausanne 2026: IS-PN02 [3494]
100 Years of Fuelling Research: How much carbohydrate do athletes really need to consume during exercise?
The effects of carbohydrate (CHO) intake on substrate metabolism, exercise capacity and exercise performance have been studied for over 100 years. From a metabolic perspective, the ergogenic effect of CHO intake is likely mediated by liver (and potentially muscle) glycogen sparing, maintenance of plasma glucose concentrations and whole-body CHO oxidation rates, such that the required exercise intensity can be sustained for a longer duration thereby delaying fatigue. Accordingly, the most recent sport nutrition guidelines recommend CHO intakes of 30-60 g.h-1 (for endurance exercise and “stop and start” sport lasting 1- 2.5 h) and 90 g.h-1 (from multiple transportable carbohydrates e.g. glucose/fructose mixtures) for “ultra-endurance” >2.5 to 3 h in duration. However, although recent anecdotal reports reflect a trend for endurance athletes to consume (and experiment with) higher rates of CHO ingestion during training and racing (i.e. 120-200 g.h-1), the efficacy of such doses is not yet substantiated by current scientific research. Rather, contemporary research suggests that the guidelines for the upper limit of CHO intake could increase from 90 to 120 g.h-1, considering that both exogenous and whole-body rates of CHO oxidation can be increased with these higher ingestion rates. Indeed, such absolute doses may also modulate important physiological determinants of performance (e.g. durability and economy) across cycling, marathon running and ultra-endurance exercise. Accordingly, this presentation will provide a contemporary review of CHO metabolism during exercise, factors affecting exogenous CHO oxidation rates (i.e. CHO blend, ratio, format, environmental considerations etc) and sport-specific research and insights from practice, before presenting an updated and more nuanced model to guide CHO personalisation strategies for endurance athletes. Directions for future research are also discussed, emphasising the need for collaborative research to study both male and female athletes during ecologically valid exercise protocols in order to better address the real-world fuelling challenges that are faced by elite athletes.
Speaker B
Mette Hansen
Aarhus University, Department of Public Health
Denmark
Read CVECSS Lausanne 2026: IS-PN02 [8340]
Under-fuelling and low energy availability: pitfalls only or are there benefits?
Athletes constantly balance on the fine line between optimal fuelling to support performance and deliberate restriction of energy or carbohydrate (CHO) intake to promote specific training adaptations or physique goals. Over the past two decades, the concept of manipulating CHO and energy availability to enhance training adaptation has gained considerable attention in endurance sports. Periodised strategies such as “train-low,” “sleep-low,” or fasted training have been proposed to amplify cell-signalling pathways linked to mitochondrial can increase phosphorylation of AMPK and promote PGC-1α expression, supporting the rationale for short-term metabolic stress as a stimulus for adaptation. Nevertheless, when these strategies are applied repeatedly in well-trained athletes, the expected benefits on performance and endurance capacity are less evident. In elite athletes, several tightly controlled interventions have failed to demonstrate superior improvements in oxidative capacity, enzyme activity or time-trial performance compared with training in a well-fuelled state. Although the acute metabolic responses to under-fuelling may initially appear appealing, reflecting amplified cellular stress signalling yet, when sustained over time, they represent the first steps along the continuum towards low energy availability and relative energy deficiency in sport. This has particular relevance for female athletes, who appear more sensitive to perturbations in energy balance, often manifesting hormonal disruption, menstrual irregularities, and altered bone and metabolic health even at modest energy deficits. Recent work has helped disentangle the effects of energy and carbohydrate restriction. Energy deficiency after exercise activates stress pathways involving elevated cortisol, inflammation, and impaired bone formation, even when glycogen levels are moderate. Conversely, short-term carbohydrate restriction, despite adequate energy intake, further suppresses bone formation and increases resorption. Together, these findings highlight that both low energy and low carbohydrate availability represent distinct stressors capable of compromising bone remodelling and recovery. This presentation will synthesise current evidence on the potential benefits and pitfalls of under-fuelling. The talk will conclude by emphasising that the true challenge is not to identify isolated benefits of restriction, but to integrate fuelling and recovery strategies that sustain adaptation and long-term performance capacity. This presentation is intended for sport scientists, applied nutrition practitioners, coaches and athletes interested in the physiological and performance implications of energy and carbohydrate availability.
Speaker C
Gareth Wallis
University of Birmingham, School of Sport, Exercise & Rehabilitation Sciences
United Kingdom
Read CVECSS Lausanne 2026: IS-PN02 [11904]
Refuelling: how do we optimise recovery of liver and muscle glycogen stores in male and female_ athletes?
The nutrition needs to facilitate recovery from exercise can vary depending on what an athlete is recovering from (e.g., type or intensity of exercise, with-in exercise fuelling, competition, training) and what they are recovering for (e.g., training adaptation, restoration of short, medium or long-term performance capacity). Given the central role of carbohydrate (i.e., glycogen in liver and muscle) as an energy substrate for most forms of exercise it is no surprise that intense research effort has been directed to how best to restore these major carbohydrate storage depots in the body after exercise. While some progress in research in female participants has been made, much of the expert guidelines for nutrition remain extrapolations from male dominated research. This presentation will provide an overview of the recent progress that has allowed us to draw research-based guidelines to inform how nutrition might support recovery of liver and muscle glycogen in male and female athletes. For example, for the liver, it is now recognised that the type of dietary carbohydrate can influence the extent of glycogen repletion, at least in the first few hours are exhaustive exercise. Indeed, provision of the monosaccharides fructose and/or galactose alongside a glucose source has been shown to stimulate a higher rate of post-exercise liver glycogen synthesis compared to when a glucose-only based carbohydrate source is provided. Complete recovery of liver glycogen within 6 hours of finishing strenuous exercise now appears possible with suitable high intake of the correct blend of carbohydrates. Recovery of muscle glycogen after strenuous exercise is less rapid and may take up to 24 hours, but still requires attention to the amount, type and timing of carbohydrate intake to facilitate an optimised resynthesis. Here, there has been some debate as to whether sex-based differences in muscle glycogen storage exist, and whether this should influence applied practice. Of course, recovery facilitated by carbohydrate nutrition does not occur in a vacuum, and from a practical perspective interaction with factors such as other nutrients or within exercise fuelling strategies means that recovery of liver and muscle glycogen needs to be considered as part of a more holistic approach to using nutrition to optimise carbohydrate status for performance. This presentation will present the latest scientific developments in this continually evolving area of sports nutrition. The talk will demonstrate how integrating nutritional science and exercise metabolism can generate translationally relevant sports science research with the potential to impact on applied practice.