Research
Hormonal
Restricting carbohydrate intake (low-carb, high-fat, or ketogenic diets) reduces the abundance and activity of intestinal SGLT1 transporters, thereby decreasing the capacity to absorb carbohydrates and increasing the risk of GI distress during competition.
If you follow a low-carb diet, your gut loses its ability to absorb large amounts of carbs. Before a race requiring high carb intake, include high-carb days to 'retrain' your gut and prevent GI issues.
ModerateSupportsMEDIUM confidence
When athletes are carbohydrate restricting; following a low-carbohydrate, high-fat, or ketogenic diet; or are reducing energy intake to lose weight, the reduced daily carbohydrate load will likely reduce the capacity to absorb carbohydrates during competition.
Why this rating
Based on animal studies (lambs) and extrapolation to humans; the author states 'no direct human studies exist' but suggests it is reasonable.
Source
Training the Gut for Athletes
Asker E. Jeukendrup · Sports Medicine · 2017
DOI 10.1007/s40279-017-0690-6
narrative_reviewCited 194×
Read the paper DOI resolved against Crossref · corpus check 2026-06-10
More from this paper
- Targeted nutritional training (specifically high-carbohydrate or high-volume intake) adapts the gastrointestinal tract by upregulating SGLT1 transporters and accelerating gastric emptying, thereby increasing exogenous carbohydrate oxidation and reducing GI distress during endurance exercise.Good
- Specific nutrient intake accelerates the gastric emptying of that specific nutrient (e.g., glucose accelerates glucose emptying, fat accelerates fat emptying) through desensitization of intestinal feedback mechanisms.Good
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