Input=Output
Your body is not a mystery. It's a machine that runs on carbs, water, and the occasional midday cry. Put the right stuff in at the right time and it performs. Put nothing in and hope for the best - well, you know how that story ends.
Basic nutrition building blocks
The numbers on the back of the pack, and what each one does.
Energy (kJ) is how food’s fuel value is measured, just like petrol for a car. The higher the kilojoules, the more energy it gives your body. For endurance athletes, knowing energy content helps you plan fuelling so you don’t run out mid-session and can keep performing strong.
Calories and kilojoules measure the same thing - how much fuel food gives your body. Tracking calories helps you match energy in with training demands so you don’t underfuel or overdo it.
Carbs are the quickest to turn into usable energy, powering every stride, pedal, or climb. They’re the difference between cruising and hitting the wall.
Sugars are the simplest carbs - absorbed fast and perfect for a mid-race boost. Too much too quickly can cause a spike and crash, so use them wisely.
Training breaks muscle down; protein builds it back stronger. Without enough, recovery slows and fatigue builds. A post-session protein hit helps you bounce back faster.
Fats provide long-lasting energy at lower intensities and help your body absorb vitamins. They’re key for everyday diet, but not the main race-day fuel.
A little is fine, but too much can slow recovery and increase inflammation. Prioritise unsaturated fats like nuts and olive oil for performance.
Fibre keeps digestion healthy and stable. Great daily, but too much before a session can mean stomach trouble mid-race.
Replace it during long sessions to avoid cramps, dizziness, or energy dips. It’s the cornerstone of electrolyte drinks and tabs.
Works with sodium to keep contractions smooth and reduce cramp risk. Losing too much (especially in heat) can leave you weak.
Calcium supports strong bones and muscle contractions. Endurance athletes who skimp risk stress fractures and weakness over time.
Supports muscle function, reduces cramp risk, and helps your body unwind after big efforts. Many athletes don’t get enough.
Caffeine sharpens focus and lowers perceived effort, making late-race fatigue feel easier. Too much though can upset your stomach or wreck your sleep.
Energy (kJ)
Just like petrol for a car.
Energy (kJ) is how food’s fuel value is measured, just like petrol for a car. The higher the kilojoules, the more energy it gives your body. For endurance athletes, knowing energy content helps you plan fuelling so you don’t run out mid-session and can keep performing strong.
Calories (kcal)
The global way of counting energy
Calories and kilojoules measure the same thing - how much fuel food gives your body. Tracking calories helps you match energy in with training demands so you don’t underfuel or overdo it.
Carbohydrates
Your high-octane fuel.
Carbs are the quickest to turn into usable energy, powering every stride, pedal, or climb. They’re the difference between cruising and hitting the wall.
Sugars
The sprint fuel.
Sugars are the simplest carbs - absorbed fast and perfect for a mid-race boost. Too much too quickly can cause a spike and crash, so use them wisely.
Protein
Your body’s repair kit.
Training breaks muscle down; protein builds it back stronger. Without enough, recovery slows and fatigue builds. A post-session protein hit helps you bounce back faster.
Fat
The slow-burner.
Fats provide long-lasting energy at lower intensities and help your body absorb vitamins. They’re key for everyday diet, but not the main race-day fuel.
Saturated fat
The heavy version of fat.
A little is fine, but too much can slow recovery and increase inflammation. Prioritise unsaturated fats like nuts and olive oil for performance.
Fibre
The gut regulator.
Fibre keeps digestion healthy and stable. Great daily, but too much before a session can mean stomach trouble mid-race.
Sodium
The main salt lost in sweat.
Replace it during long sessions to avoid cramps, dizziness, or energy dips. It’s the cornerstone of electrolyte drinks and tabs.
Potassium
The muscle conductor.
Works with sodium to keep contractions smooth and reduce cramp risk. Losing too much (especially in heat) can leave you weak.
Calcium
The bone strengthener.
Calcium supports strong bones and muscle contractions. Endurance athletes who skimp risk stress fractures and weakness over time.
Magnesium
The relax-and-recover mineral.
Supports muscle function, reduces cramp risk, and helps your body unwind after big efforts. Many athletes don’t get enough.
Caffeine
The performance boost.
Caffeine sharpens focus and lowers perceived effort, making late-race fatigue feel easier. Too much though can upset your stomach or wreck your sleep.
The 5 fundamentals of a healthy diet
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The day-to-day
Balanced meals are your base and lay the foundation for long-term performance. Build most of your meals from fruits, vegetables, whole grains, lean protein, and healthy fats.
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Performance Fuel
Fuelling before, during, and after key sessions keeps you energised, reduces fatigue, and supports progress. Underfuelling can limit adaptation and increase injury risk.
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Hydration & electrolytes
Fluids and electrolytes play a part in how your muscles work and how long you can keep going. Start hydrated, drink to thirst, and sip regularly, especially in the heat or on long sessions.
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Supplements
Electrolytes, caffeine or recovery powders can help with the details. They are not a substitute for proper fuelling. Get the basics right first, then test what works for you in training.
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Timing & strategy
When you fuel is just as important as what you eat. Carbs before training power your effort, carbs during keep you going, and carbs with protein after help rebuild. Post-session fuelling is the key to recovery and progress.
Questions we get asked
When should you be eating?
Timing matters as much as what you eat. Fuel with carbs 1-3 hours before and during sessions to power your effort, and combine carbs with protein after to recover and rebuild. Small, regular snacks between meals keep energy steady.
Have you eaten enough?
Signs of underfuelling can include early fatigue, dizziness and slow recovery. As a rough guide, aim for 30 to 60 g of carbs an hour on sessions over an hour, working up to 60 to 90 g on long ones once your gut is used to it, with balanced meals around them. If you are always hungry, sore or tired, look at how much you eat, and speak to a sports dietitian if it carries on.
What do recovery meals look like?
A strong recovery meal combines carbs to restore energy, protein to repair muscles, and colourful veg for vitamins and minerals. Think rice with lean meat and vegetables, or a smoothie with fruit and protein. Simple, balanced, and quick.
Adapting to intolerances?
Endurance nutrition is flexible. Gluten-free athletes can lean on rice, potatoes, and maize. Dairy-free? Choose plant-based protein powders or nut milks. Always test products in training, not on race day, to find what works for your gut.
Daily fuel, by training load
Per kilogram of body weight, per day. Pop your weight in to see grams.
| Training that day | Carbs a day | Fat a day |
|---|---|---|
| Rest or easy day | 3g per kg | 1–3g per kg |
| About an hour, moderate | 5–7g per kg | 1–2g per kg |
| 1 to 3 hours of training | 6–10g per kg | 2–3g per kg |
| 4 to 6 hours, split sessions | 8–12g per kg | 3g per kg |
| Protein, every day: 0.4 g per kg, 3 to 6 times a day, whatever the training. | ||
After a session
- Within 20 to 30 minFast carbs and easy protein: 1 to 1.2 g of carbs and 0.4 g of protein per kg.
- Every 2 to 3 hRepeat that mix while you recover.
- Within 2 hA proper balanced meal.
General guidance, not medical advice. Still not sure? Ask us.
Next up: race day
What to eat in the days before, on the morning, and on the move. Then build the kit.