[Contributed by Valentine De Pascale]
Whether you’re grinding away on Zwift, logging treadmill miles, or testing yourself on the open road, endurance performance is, at its core, a fuelling competition.
Nutrition is often called the fourth discipline of endurance sport — and for good reason. It’s not only the difference between a strong finish and a painful DNF, but between a resilient, healthy body and one that’s run down or injury-prone.
1. Fuelling Long Sessions: Indoors vs Outdoors
Indoor training is deceptively tough. Without airflow, sweat rates can be two to three times higher than outdoors, which means hydration and sodium intake are critical — even when you don’t feel thirsty.
The upside? Indoors, you can control every variable. Line up bottles, gels and real food, and replicate your fuelling strategy without worrying about weight or logistics.
Outdoors, long sessions become race rehearsals. This is where you practice carrying nutrition, swapping bottles, and eating on the move. It’s also where you train your gut — repeated exposure to carbs under race-like stress improves tolerance and absorption, a concept known as training the gut.
Tip: Use indoor sessions to fine-tune your strategy, and outdoor sessions to pressure-test it. Both matter.
2. Carb Loading = Fat De-loading
Carbohydrate loading maximises glycogen — your body’s stored energy. The fuller your tank, the longer you can delay fatigue.
But simply piling carbs on top of your usual diet often leads to feeling bloated and sluggish. The smarter approach is to think of carb loading as fat de-loading.
Since one gram of fat contains more than double the calories of a gram of carbohydrate, reducing fats in the 36–48 hours before an event creates the space for extra glycogen without unnecessary calorie overload.
Tip: Lower fats slightly before your event while increasing carbs — this helps you load efficiently and feel lighter on race day.
3. Calories Matter: Every Day
Your body is an engine — and engines don’t run on empty.
Endurance athletes can burn between 600–1,200 kcal per hour, depending on intensity and individual physiology.
Chronic under-fuelling compromises recovery, hormones, immunity, bone health and overall adaptation. Energy availability drives progress: fuel well and you get stronger; under-fuel and your training plateaus.
Tip: Treat fuelling as part of your training — not separate from it. Energy intake supports every adaptation you’re chasing.
4. Carbs + Sodium = Fluid Absorption
Hydration is more than drinking water. Without sodium, fluids don’t absorb efficiently and can pass straight through. Pairing sodium with carbohydrates enhances uptake, giving you energy and hydration.
Research shows that a 6–8% carbohydrate solution with added sodium — the standard in most sports drinks — is optimal for both absorption and performance.
5. Real Food First
Sports nutrition products are designed for convenience, not as the foundation of your diet. Real food provides the nutrients your body needs for long-term health and recovery.
Tip: Think in terms of:
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Training and race nutrition: functional and temporary
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Daily nutrition: foundational and consistent
Final Word
Science and structure are essential, but so is mindset.
If you’ve set yourself a big goal — a marathon, an Ironman, or your longest ride yet — your food choices should reflect that ambition.
Be intentional with what you put on your plate. Impulsive choices might get you through the day, but consistent, nourishing foods build the foundation for performance and long-term health. Nutrition is an act of care — one that aligns with the athlete you want to become.
At the same time, remember that food is more than fuel. It’s connection, culture, and joy. Shared meals and celebrations are as vital to wellbeing as the most precise fuelling plan.
High goals demand high standards, not perfection. The happiest, healthiest athletes are those who can stay intentional with their nutrition while embracing the social side of food. That balance sustains both performance and life.
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Valentina “Fuelling Endurance” MRSPH-UKSCA
Head of Nutrition
Food & Nutrition Educator in UK’s schools and Endurance Sports
Currently doing MSc in Performance Nutrition-specialising in Female Endurance Athletes
Triathlon Coach
Finalist Best Online Coach by UKCoaching 2024
4x Ironman finisher, Ultra-triathlete and Ultra-runner
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