13.1 miles is serious distance. Unlike a 5K where nutrition barely matters or a marathon requiring complex carb-loading, the half marathon sits in between - long enough that fuelling strategy genuinely affects your race, but not so long that you need to stress about every detail.
Get your pre-race nutrition right and you'll have steady energy through all 13 miles. Get it wrong and the final 5K becomes a sufferfest.
The Half Marathon Challenge (The Science)
Most runners take 1.5-2.5 hours to complete a half. Your body stores ~2,000 calories of glycogen - enough for 90-120 minutes of running. At half marathon duration, you'll use 60-80% of glycogen stores. Pre-race nutrition is about maximising those stores so you can maintain pace throughout.
The Days Before
Modified Carb Loading (Evidence-Based)
Research from the ACSM confirms carb loading benefits events lasting >90 minutes. For a half marathon, you don't need the aggressive 10-12g/kg protocol - a modified approach works.
7-10g carbs per kg bodyweight daily for 24-36 hours before events of this duration. For a 70kg runner, that's 490-700g carbs. In practice: choose pasta over salad, have rice with dinner, don't avoid bread. Studies show this can increase glycogen stores by 20-40%.
Night Before the Race
Your most important pre-race meal. Classic options:
- Pasta with tomato-based sauce (not creamy) and lean protein
- Rice with chicken or fish
- Potato-based meal with protein
- Risotto (without too much cheese)
Eat at a reasonable time (6-7pm) so you have time to digest before bed. Avoid very spicy, very fatty, or high-fibre meals. No alcohol - it disrupts sleep and dehydrates you.
Race Morning
3-4 Hours Before Start
Your main pre-race breakfast. This is the meal that will fuel your race. 400-600 calories, mostly carbohydrates, moderate protein, low fat and fibre.
1-2 Hours Before
Top-up snack if needed. Something small and easily digestible. Many runners skip this if their earlier breakfast was substantial.
30-60 Minutes Before
Final small snack if you feel you need it. Half a banana, few sweets, or a few sips of sports drink. Otherwise, just water.
Best Pre-Half Marathon Breakfasts
Hydration Strategy
Start hydrating the day before - drink water consistently, not just morning of the race.
- Day before: Drink 2-3 litres throughout the day
- Morning of: 400-500ml with breakfast
- Before start: Small sips, stop 30 mins before so you don't need the toilet
- Urine check: Should be pale yellow, not dark or completely clear
Fuelling During the Race (Research)
Aim for 30-60g carbs per hour for endurance events over 60 minutes. For a 1.5-2.5 hour half marathon, that typically means 1-2 natural gels during the race - around miles 5-6 and 9-10. GI distress affects 30-50% of runners, so test your race fuel in training. Don't try new natural gels or drinks on race day.
Half Marathon Nutrition Mistakes
- Eating too much morning of: Heavy stomach = slow running
- Eating too little: You'll hit the wall around mile 10
- Trying new foods: Race day is not for experiments
- Skipping the night-before meal: That dinner matters
- Drinking too much water: Can cause cramping and toilet stops
- High fibre before race: Emergency toilet stops are not fun mid-race
- Caffeine overdose: One coffee is fine, three might cause issues
Example Race-Morning Schedule
For a 9am race start:
- 5:30am: Wake up, bathroom, start drinking water
- 5:45am: Breakfast (porridge with banana, coffee)
- 6:30am: Travel to race venue
- 7:30am: Arrive, collect number, use toilets
- 8:00am: Small snack if needed (half banana), final toilet visit
- 8:30am: Warm-up jog, dynamic stretches
- 8:50am: Head to start corral
- 9:00am: Race!
Evidence-Based Pre-Half Marathon Summary
- Modified carb loading: 7-10g/kg carbs for 24-36 hours before (can increase glycogen by 20-40%)
- Carb-rich dinner the night before (pasta, rice, potatoes)
- Breakfast 3-4 hours before: 400-600 calories, mostly carbs
- Stay hydrated: 2% dehydration impairs endurance by ~10%
- Use only foods you've tested in training - GI distress affects 30-50% of runners
- During race: Aim for 30-60g carbs/hour for events >60 minutes
- Visit the toilet before the start - multiple times if needed
After you finish, recovery nutrition becomes important. See our guide on what to eat after a half marathon.
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