Ormsbee et al. [1] recently published a comprehensive review article on the effects of pre-exercise nutrition on endurance performance. As it often happens when you look at the primary scientific literature, the situation is complex and cannot be boiled down to a few simple guidelines, as popular science and other self-declared experts often want us to believe. Some of the questions they tried to answer are:
- Does pre-exercise carbohydrate ingestion increase performance? What are the effects of timing?
- What are the benefits of consuming starches?
- How does the consumption of a high-fat meal pre-exercise affect performance?
- What are the effects of short- and long-term fat adaptation?
- How does adding protein to carbohydrate meals affect performance?
- How does caffeine affect performance? What are the effects of timing?
- Does pre-exercise ingestion of beetroot juice enhance performance?
In general the consumption of carbohydrate-rich meals pre-exercise benefits performance. The answer is not as simple for starches. The effect depends on how they are modified. The effect of high-fat meals is unclear. And both caffeine and beetroot juice enhance performance, but the effects depends on genetic factors and/or training.
[1] Michael J. Ormsbee, Christopher W. Bach, and Daniel A. Baur, Pre-Exercise Nutrition: The Role of Macronutrients, Modified Starches and Supplements on Metabolism and Endurance Performance, Nutrients, 6(5): 1782–1808, 2014.