Pre-exercise timing (the 3-hour rule) is secondary to individual digestive tolerance; it is necessary to train the digestive system for exertion through repetition and gradual progression.

noli's read

This advice aligns with current sports nutrition recommendations, which emphasize training the gastrointestinal tract. Meta-analyses and systematic reviews (notably in the Journal of the International Society of Sports Nutrition) confirm that intestinal 'absorption capacity' can be improved through repeated exposure to nutrients during exercise. The 3-hour rule is a generalization that does not account for meal composition (glycemic index, fiber, lipids) or interindividual metabolic differences. While the idea of testing one's routine during training is a practice validated by coaches and nutritionists to avoid gastrointestinal issues on race day, it is true that digestibility varies greatly from one person to another. There is no evidence that a fixed 3-hour delay is optimal for everyone; the concept of 'personalized tolerance' is therefore scientifically more relevant than the temporal dogma.

the sources

No named source held this one up — that absence is part of the verdict.