Trail race fueling: how much should you eat and drink?

When hunger arrives during a race, it is often already late. Glycogen stores are dropping, focus declines, the legs respond less clearly, and every acceleration becomes more expensive. Fueling should begin early, often within the first 30 to 45 minutes.

The idea is simple: take small amounts regularly instead of trying to catch up all at once. Eating every 20 to 30 minutes works well for many runners, as long as that rhythm has been tested in training.

For a short outing or easy race, 30 to 40 g of carbohydrate per hour may be enough. On longer or harder trail races, many runners aim closer to 50 to 70 g per hour. Some go up to 90 g per hour, but only with trained digestion and products they tolerate well.

Carbs can come from gels, drink mixes, fruit purees, bars, fruit jellies, or simple foods. The format matters less than consistency and tolerance. A perfect plan on paper is useless if you cannot digest it while running.

Drinking matters, but drinking too much plain water can also create problems. Depending on heat, sweat rate, and intensity, a starting benchmark is often around 400 to 800 ml per hour, adjusted to the conditions.

Sodium helps replace part of what you lose through sweat. Needs vary widely, but sports drinks, electrolyte tablets, or salty foods can help during long, hot, or very sweaty races.

Under 90 minutes, the main goal is to start hydrated and carry a simple carb option if the effort is intense. Between 90 minutes and 3 hours, structured intake becomes useful: regular carbs, frequent small sips, and extra margin if it is hot.

Beyond 3 hours, fueling becomes a real strategy. You can alternate sweet and salty, liquid and solid, eat more during easier sections, and avoid trying an unknown product at an aid station.

Your digestive system can be trained like your legs. Long runs are the best time to test quantities, timing, products, drink concentration, and your ability to eat while climbing or descending.

Track what works: number of gels, fluid volume, weather, gut comfort, and energy at the end of the run. After a few tests, you will have more than a theory: you will have a personal plan.

Waiting until you bonk, drinking only water, mixing too many new products, eating too much fiber or fat right before the race: these are common traps. Trail fueling should be simple, repeatable, and adapted to the terrain.

The best strategy is the one you can still follow when you are tired. Prepare portions, know your approximate timing, and always keep a backup option in case an aid station does not match what you expected.