Updated 25/05/2026
A high-carbohydrate breakfast providing substantial fuel failed to increase muscle or liver glycogen stores in well-trained endurance cyclists, according to new research that challenges common assumptions about pre-exercise fuelling strategies. The study suggests that athletes who maintain regular training and adequate carbohydrate intake may already have maximized their glycogen storage capacity.
Glycogen Response to High-Carbohydrate Breakfast
Changes in liver and muscle glycogen over 3 hours in trained cyclists
cyclists studied
body weight given
or liver glycogen
Source: PMID 41115061, 2024 | Georgian Medical Journal News
Well-Trained Athletes Start with Full Tanks
The study (PMID: 41115061) recruited 16 well-trained male cyclists who underwent morning testing after an overnight fast. Researchers used magnetic resonance spectroscopy to assess liver glycogen non-invasively and muscle biopsies to measure skeletal muscle glycogen stores.
According to the research team (PMID: 41115061), “these cyclists likely arrived glycogen-replete due to their regular endurance training and adequate carbohydrate intake the day before.” The study authors noted that regular endurance training increases the body’s capacity to store glycogen, while consistent carbohydrate intake maintains these elevated stores. For insights into clinical applications of sports nutrition research, recent studies continue to refine our understanding of athlete metabolism.
Storage Capacity Reaches Physiological Ceiling
Despite receiving 3 grams of carbohydrate per kilogram of body weight—a substantial breakfast load—neither muscle nor liver glycogen increased measurably over the three-hour observation period, according to the study findings (PMID: 41115061). Muscle glycogen remained unchanged from baseline values, which were already elevated even after the overnight fast.
The findings align with physiological principles showing that when glycogen stores approach their maximum capacity, additional carbohydrate cannot be stored regardless of intake volume. This phenomenon occurs because glycogen synthesis becomes saturated when storage sites are already occupied. Research published in sports medicine journals continues to explore these metabolic limitations, with implications for performance optimization strategies.
Implications for Pre-Exercise Fuelling
The research challenges conventional pre-exercise nutrition recommendations that emphasize large carbohydrate meals before training or competition. For well-trained athletes who maintain consistent training schedules and adequate daily carbohydrate intake, additional pre-exercise carbohydrate loading may offer limited benefit.
Athletes who train regularly and consume adequate carbohydrates may benefit more from maintaining steady intake patterns rather than emphasizing single large meals.
When liver and muscle glycogen stores are already near their physiological ceiling, additional carbohydrate cannot be stored, even in large amounts.
— Research team, PMID 41115061 (2024)
Key takeaways
- High-carbohydrate breakfast (3g/kg body weight) failed to increase glycogen in trained cyclists
- Regular training and adequate daily carbohydrate intake maintain near-maximal glycogen stores
- Pre-exercise carbohydrate loading may be unnecessary for well-trained athletes with consistent nutrition
Frequently asked questions
Why didn’t the high-carb breakfast increase glycogen stores?
The trained cyclists already had near-maximal glycogen stores from regular training and adequate daily carbohydrate intake. When storage capacity is saturated, additional carbohydrate cannot be stored regardless of intake amount.
Does this apply to recreational athletes?
The study focused on well-trained cyclists who likely maintain consistently high glycogen stores. Recreational athletes with lower training volumes or inconsistent carbohydrate intake may still benefit from pre-exercise carbohydrate meals.
Should athletes skip pre-exercise carbohydrate meals?
Not necessarily. While additional storage may be limited, pre-exercise carbohydrates can still provide readily available glucose for immediate energy needs and help maintain blood sugar during prolonged exercise.
Future research should examine whether similar findings apply across different training levels and sports disciplines, while also investigating the optimal timing strategies for carbohydrate intake in various athletic populations. Understanding individual glycogen storage capacity could help personalize nutrition recommendations for competitive athletes seeking performance optimization.
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Medically reviewed by Prof. Giorgi Pkhakadze, MD, MPH, PhD. Spotted an error? Contact the editorial team.
