Carbohydrate intake during endurance training and competition is correlated with improved performance and longer exercise time, with up to ~90 grams per hour (or up to ~120 grams per hour for some athletes) being optimal for competitive endurance athletes. The primary mechanism by which carbohydrate benefits endurance is through increased carbohydrate delivery and oxidation for ATP (energy) production. Some athletes struggle to meet these carbohydrate recommendations BUT with proper gut training, carbohydrates can actually help maintain the integrity of the gut, reduce intestinal permeability and associated GI distress.
There are, however, scenarios in which a high rate of carbohydrate intake is not feasible (e.g. individual tolerance, gastric emptying rates, specific carb digestibility, hydration, heat, etc). Of course fat and protein also provide energy but carbohydrate is oxidized more efficiently (lower oxygen cost) and is essential for supporting higher intensity efforts. While an athlete’s primary energy intake during an event should come from carbs, solid foods containing carbs with small amounts of fat and/or protein may help offset hunger and flavor fatigue during endurance events > 6 hours.
It is possible that protein intake during endurance activity > 6 hours may also help enhance recovery, but the type (e.g. complete or BCAAs) and amount of protein that might provide benefit remains unclear and tolerance is likely to be highly individual . During ultra-endurance efforts, the pace may be slow enough to permit the body to rely more heavily on fat oxidation, compared to carbohydrate. Solids and liquids containing fat may also be tolerable at these lower intensities for prolonged periods; however, risk of glycogen depletion must still be managed by taking in adequate carbohydrate (> 60-90 g per hour on average) during these events.
To ensure your greatest chance of success in an ultra-endurance event, it’s important to experiment with a variety of liquids, gels, and solids to determine individual preference, palatability, and GI tolerance. A portion of these foods and drinks can also provide protein and fat if well tolerated, and should also provide necessary sodium to maintain hydration. In general, if the event is longer than >6 to 8 hours in duration and/or relatively low intensity, athletes may be able to ingest solid food options containing macronutrients other than carbohydrates. So while carb-rich options that contain some fat and/ or protein (e.g. PB&J, granola bars, dates stuffed with nut butter) are likely tolerated, athletes should avoid foods that are particularly HIGH in protein, fat, fiber, and fermentable oligo di- monosaccharides, and polyols (FODMAPS).
PMID 24951297, 30056753, 11356768, 24791922, 31699159, 26891166, 30558350; 24791914; 30943823