In trail running, nutrition isn't a detail — it's the fourth pillar of performance alongside training, gear and mental strength. A bad fueling strategy can turn a well-prepared race into a nightmare. Here's everything you need to know.
The basics: what your body needs
During endurance exercise, your body burns two main fuels:
- Carbohydrates (muscle + liver glycogen): fast energy, but limited stores (~90 min of intense effort)
- Fats: slow and virtually unlimited energy, but less efficient at high intensity
The goal of race nutrition is simple: replace the carbs you burn to delay glycogen depletion (the infamous "wall").
Before the race: carb loading
D-3 to D-1: supercharging your stores
Increase your carb intake to 70% of calories (Burke et al., 2011): pasta, rice, bread, potatoes, fruit. Reduce fiber (no legumes, fewer raw vegetables) to avoid GI issues on race day.
Race morning
Eat 3 hours before the start. A meal you've tested in training:
- White bread or rice cakes + jam or honey
- 1 ripe banana
- Tea or coffee (careful, coffee is a diuretic)
- Optional: 1 applesauce pouch or plain yogurt
Avoid: eggs, butter, whole grains, orange juice (acidity).
Key takeaway: Pre-race nutrition must be tested, simple, and familiar. Race day is not the time for experiments. Your stomach needs to be able to process this meal quickly without creating digestive problems an hour later.
During the race: km-by-km strategy
What to eat?
The choice between gels and solid food depends on intensity and duration:
Races < 2h (short trail): water + 1-2 gels is enough. Absorption is fast and the stomach isn't stressed.
Races 2-5h (medium trail): alternate gels and solid food. Plan for 200-300 kcal/h:
- 1 gel every 45 min (80-100 kcal each)
- Energy bars cut into pieces
- Dried fruit (dates, apricots), fruit paste
- At aid stations: banana, cheese, gingerbread
Races > 5h (ultra): solid food becomes essential as gels often cause nausea over long periods. Add salty options: chips, soup, ham, pretzels. Aim for 250-350 kcal/h.
When to eat?
Start eating within the first 30-45 minutes, even if you're not hungry. The stomach absorbs better when it's not empty. Then eat something small every 20-30 minutes.
Universal rule: In trail running, eat before you're hungry and drink before you're thirsty. Hunger and thirst are late signals — when you feel them, your energy and hydration reserves are already declining.
💡 Practical tip: Power-hiked climbs are the ideal time to eat. Intensity is lower, your stomach works better, and you avoid the discomfort of eating while sprinting. Build this strategy into all your long training runs.
Hydration: the other half of the equation
Dehydration of 2% body weight reduces performance by 10-20% (ACSM Position Stand, 2007). But drinking too much is also dangerous (hyponatremia).
How much to drink?
- Cool weather (< 15°C / 59°F): 400-500 ml/h
- Mild weather (15-25°C / 59-77°F): 500-700 ml/h
- Hot weather (> 25°C / 77°F): 700-1000 ml/h
Water, sports drink, or both?
For efforts > 1.5h, an isotonic drink (30-60 g carbs/L + sodium) is better than water alone. It provides energy AND electrolytes. Put it in one bladder and keep plain water in the other.
After the race: the recovery window
Within 30 minutes
This is the "metabolic window" when your body absorbs nutrients best:
- Recovery drink (carbs + protein, 3:1 ratio)
- Or: chocolate milk, banana-protein smoothie, yogurt + honey
Within 2 hours
Complete meal rich in carbs and protein: pasta with meat sauce, rice + chicken, or pizza. Yes, post-trail pizza is a classic for good reason.
Key takeaway: Post-race nutrition recovery is just as important as training itself. These two hours after the race are critical — your body is primed to absorb nutrients and begin muscle repair. Don't skip it just because you're tired.
The 4 fatal nutrition mistakes
1. Testing new nutrition on race day
Every gel, bar or drink must be tested in training. Your stomach needs time to adapt.
2. Eating only sweet food
Beyond 3h of effort, your palate tires of sweetness and your stomach protests. Plan for salty options.
3. Not eating on climbs
Power-hiked climbs are the perfect time to eat — intensity is lower and the stomach works better.
4. Waiting until you're hungry
Hunger during a race is a late signal. By the time you feel it, your glycogen stores are already in freefall.
Plan your nutrition with RaceDayLab
Our Fuel Planner automatically calculates your calorie, hydration and fueling needs based on your race, speed and weather conditions.
Related articles
Ready to prepare your next race?
Use our free tools: pace calculator, nutrition planner, gear finder.
Calculate my pace