Research
Energy balance
Consuming carbohydrates 3-4 hours before exercise significantly increases muscle and liver glycogen content and improves endurance performance compared to fasting, whereas consuming carbohydrates 30-60 minutes before exercise causes transient metabolic perturbations (hyperinsulinemia, hypoglycemia) that do not impair performance and may be beneficial.
Eat a carbohydrate-rich meal 3-4 hours before your event to maximize energy stores. If you need to eat closer to exercise (30-60 mins), choose a small snack or drink to avoid stomach issues; the resulting blood sugar dip is temporary and won't hurt your performance, and the fuel will likely help you.
GoodSupportsHIGH confidence
A CHO-rich meal consumed 4 h before exercise significantly increases muscle and liver glycogen content... Furthermore, the intake of a substantial amount of CHO (approximately 300g) 4 h before exercise by fasted subjects improved the time taken to complete a fixed amount of work... Compared with the unfed state, the consumption of CHO in the 30-60min period before exercise causes a pronounced elevation in plasma glucose and insulin concentrations... However, a review of the literature reveals that this is the only study to find reductions in performance capacity after the ingestion of CHO in the hour before exercise. Other investigations have found either no detrimental effect or improvements in performance ranging from 7 to 20 %
Why this rating
The paper is a review citing multiple controlled trials and isotope studies, though it notes direct performance studies are rare.
Source
Effect of meal frequency and timing on physical performance
John A. Hawley et al. · British Journal Of Nutrition · 1997
DOI 10.1079/bjn19970107
narrative_reviewCited 100×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- Ingesting carbohydrates during prolonged exercise improves performance by maintaining plasma glucose and sparing liver glycogen, regardless of whether the CHO is consumed in a single bolus or multiple smaller feedings, as long as the total amount is sufficient.Good
- Consuming carbohydrates immediately after exercise maximizes the rate of muscle glycogen re-synthesis, which is critical when recovery time between sessions is short (4-8 hours), although total glycogen storage over 24 hours is similar regardless of feeding frequency if total intake is sufficient.Good
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