26.2 miles. The distance where nutrition can make or break your race. Unlike shorter events where you can get by on stored glycogen, a marathon will drain your energy reserves completely - unless you start with full tanks and refuel along the way.
Marathon nutrition isn't just about race morning. It's about the days leading up to the start line. Here's the complete guide to fuelling your marathon properly.
The Marathon Energy Reality (The Science)
Your body stores approximately 2,000 calories of glycogen in muscles and liver - enough for 90-120 minutes of running at marathon pace (roughly 18-20 miles). After that, you either hit "the wall" or you've fuelled properly during the race. Studies show glycogen depletion is the primary limiter in marathon performance. Pre-marathon nutrition maximises those starting stores; race nutrition keeps you going to the finish.
Carb Loading: The Science
What Carb Loading Actually Means (Evidence-Based)
Carb loading is effective for events lasting >90 minutes. It's not eating pasta until you're sick the night before. It's systematically increasing your carbohydrate intake over 36-48 hours while reducing training, allowing your muscles to supercompensate and store extra glycogen.
Research Target: 10-12g of carbohydrates per kg bodyweight daily for 36-48 hours before the marathon (ACSM recommendation). For a 70kg runner, that's 700-840g of carbs per day. This is significantly more than normal eating - studies show it can increase glycogen stores by 25-100%.
Important: Reduce fibre intake during carb loading to avoid digestive issues. Choose white rice over brown, white bread over wholemeal.
Week Before the Marathon
7-4 Days Before
Eat normally, slightly increasing carbs. Focus on familiar, easy-to-digest foods. Start reducing fibre. Stay well hydrated. Your final long run and significant training should be done by now (taper week).
3-2 Days Before (Carb Loading Begins)
Increase carbs significantly. Eat frequently - 5-6 times a day. Every meal and snack should contain substantial carbs. Rice, pasta, bread, potatoes, cereals, fruit. Reduce fat and protein slightly to make room for all the carbs.
Day Before (Final Day of Loading)
Continue high carb intake. Eat an early dinner - 5-6pm at the latest. Choose something familiar and low-fibre. Classic choice: pasta with plain tomato sauce. Drink plenty of water. Get to bed early.
Race Morning
Your most important pre-race meal. Timing is crucial - you need 3-4 hours for proper digestion.
3-4 Hours Before Start
Breakfast of 400-600 calories, mostly carbohydrates. This tops up liver glycogen (which depletes overnight) and ensures you start fully fuelled. Low fat, low fibre, familiar foods only.
Best Marathon Breakfasts
Final Hours
- 2 hours before: Small snack if needed - half a banana, few sweets
- 1 hour before: Sip water, use toilet, dates or natural energy gel if part of your plan
- 30 mins before: Final toilet visit, small sips of water, get to start corral
Hydration Strategy
Start hydrating days before, not race morning:
- 48 hours before: Drink 2.5-3 litres daily
- Night before: Stop drinking 2-3 hours before bed to avoid overnight toilet trips
- Morning: 400-500ml with breakfast, stop 60-90 mins before start
- Urine check: Pale yellow = ready. Dark = drink more. Clear = potentially overhydrated
Fuelling During the Marathon (ISSN Guidelines)
Unlike shorter races, you MUST fuel during a marathon. Your pre-race stores won't last 26.2 miles. Aim for 30-60g of carbohydrates per hour during endurance exercise lasting >2.5 hours. With gut training, some athletes can tolerate up to 90g/hour using multiple carbohydrate sources (glucose + fructose).
Critical: Test your race-day fuelling strategy in training. Never use a new gel, food, or drink for the first time on race day. Gastrointestinal distress affects 30-50% of marathon runners - training your gut is essential.
Marathon Nutrition Mistakes
- Overeating night before: One big meal doesn't compensate for poor nutrition all week
- Too much fibre: The marathon portaloo queue is not where you want to be
- New foods on race day: Your stomach doesn't need surprises at mile 18
- Drinking too much water: Hyponatremia (low sodium) is a real risk
- Skipping breakfast: You need those final carbs and hydration
- Not testing race fuel: Find what works in training, not the race
Example Race-Week Schedule
For a Sunday marathon:
- Monday-Thursday: Normal eating, slight carb increase, reduce training
- Friday-Saturday: Carb loading - high carb meals, low fibre, stay hydrated
- Saturday dinner: Pasta, rice, or familiar carb meal. Early (5-6pm).
- Sunday 4am: Wake up, bathroom, light breakfast
- Sunday 4:30am: Eat breakfast (porridge/toast)
- Sunday 6-7am: Travel to race, sip water
- Sunday 8am: Arrive, collect number, toilets, warm up
- Sunday 9am: Race!
Evidence-Based Pre-Marathon Summary
- Carb load for 36-48 hours before (ACSM: 10-12g/kg bodyweight) - increases glycogen by 25-100%
- Reduce fibre, choose white carbs over brown
- Familiar foods only - no experiments
- Early dinner night before (5-6pm)
- Breakfast 3-4 hours before start (400-600 cal)
- Stay hydrated: 2% dehydration impairs performance by ~10%
- During race: Aim for 30-60g carbs/hour (up to 90g with gut training)
- Test race fuel in training - GI distress affects 30-50% of runners
After you cross that finish line, recovery nutrition is crucial. See our guide on what to eat after a marathon.
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