Research
Hormonal
Ingesting carbohydrate 30–60 minutes before exercise does not impair performance and may enhance it, despite causing metabolic shifts like increased carbohydrate oxidation and inhibited fat oxidation.
You can safely eat carbohydrates 30–60 minutes before your event. It will not hurt your performance, and it might help. Just ensure you eat enough (e.g., up to 100g) without causing stomach distress. If you are prone to blood sugar crashes, test this in training.
GoodRefutesHIGH confidence
On balance, there appears to be little evidence to support the practice of avoiding carbohydrate ingestion in the hour before exercise, provided sufficient carbohydrate is ingested.
Why this rating
Consistent findings across multiple studies (Gleeson, Sherman, Thomas, Kirwan) showing unchanged or enhanced performance.
Source
Pre-exercise carbohydrate and fat ingestion: effects on metabolism and performance
Mark Hargreaves et al. · Journal of Sports Sciences · 2003
DOI 10.1080/0264041031000140536
narrative_reviewCited 178×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- Ingesting 10–12.5 g carbohydrate per kg body mass per day for 1–7 days prior to competition increases muscle glycogen to 170–180 mmol/kg wet mass and enhances endurance performance in events lasting 90 minutes or more.Good
- Ingesting 200–300 g of carbohydrate 3–4 hours before exercise enhances endurance performance by increasing muscle and liver glycogen and maintaining blood glucose, with effects persisting for up to 6 hours.Good
- Increasing fat availability before exercise (via high-fat diet or fat infusion) reduces carbohydrate utilization but does not improve exercise performance.Good
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