You’ve put in the training — the long runs, the tempo sessions, the 6am Saturday mornings in the rain. Your legs are ready for marathon day. But if your nutrition plan is “eat a big pasta dinner the night before and hope for the best,” you’re about to discover why so many marathoners hit the wall at mile 20. Proper fuelling isn’t just for elite runners. It’s the difference between a finisher’s photo you’re proud of and one where you look like you’ve been rescued from sea.
In This Article
- Why Marathon Nutrition Is Different
- The Energy Systems You Need to Understand
- 8 Weeks Out: Building the Foundation
- 4 Weeks Out: Fine-Tuning
- Race Week: The Carb Load
- Race Morning: The Pre-Race Meal
- During the Marathon: What to Eat and When
- Hydration Strategy
- Post-Marathon Recovery Nutrition
- Common Nutrition Mistakes
- Frequently Asked Questions
Why Marathon Nutrition Is Different
A half marathon is hard, but most runners can get through one on normal eating habits and some water. A full marathon is a different beast. You’re running for 3-5+ hours, burning roughly 2,500-3,500 calories, and your body’s glycogen stores — the primary fuel for sustained effort — run out at around the 90-minute mark. After that, you’re either topping up fuel mid-run or you’re slowing down whether you want to or not.
The Bonk (Hitting the Wall)
Every marathon runner dreads it. Around mile 18-22, your glycogen is depleted, your blood sugar drops, and your body switches to burning fat — which provides energy but much more slowly. Your legs feel like they’re filled with sand. Your brain tells you to stop. This is “the bonk,” and while training helps push it back, nutrition is what prevents it entirely.
Why You Can’t Wing It
You wouldn’t run 26.2 miles without training your legs. Don’t try to run it without training your gut. Your digestive system needs practice processing fuel during exercise, and race day is the worst possible time to discover that a particular energy gel makes you feel sick. The NHS’s guide to eating for sport covers the fundamentals of eating for active lifestyles.
The Energy Systems You Need to Understand
You don’t need a sports science degree, but understanding two numbers helps everything else make sense.
Glycogen Stores
Your muscles and liver store about 1,600-2,000 calories of glycogen (the stored form of carbohydrate). During marathon-pace running, you burn roughly 60-100g of carbohydrate per hour, depending on your pace and weight. At those rates, your stores last about 90-120 minutes. After that, you need to eat.
Fat as Fuel
Your body also burns fat during endurance exercise, but the process is slower and less efficient at marathon pace. Trained runners burn a higher proportion of fat (which is good — it extends glycogen), but even elite athletes can’t run a marathon on fat alone. The goal is to use nutrition to keep your glycogen topped up while your body burns a mix of both fuels.
The Practical Implication
If you’re running a 4-hour marathon, you need to consume roughly 30-60g of carbohydrate per hour after the first hour. That’s 90-180g total during the race. Energy gels typically contain 20-25g of carbs each, so you’re looking at 4-7 gels during the race, plus whatever the water stations provide. Our guide to energy gels covers the options available in the UK.
8 Weeks Out: Building the Foundation
This is where most nutrition plans start, and it’s less about dramatic changes than about building habits.
Daily Carbohydrate Intake
During heavy training weeks (40-50+ miles), aim for 5-7g of carbohydrate per kilogram of body weight per day. For a 70kg runner, that’s 350-490g of carbs daily — substantially more than most people eat normally.
Good sources:
- Porridge — the staple UK runner’s breakfast. About 50g carbs per 80g serving (dry weight)
- Pasta — about 75g carbs per 100g (dry weight). The evening before long runs.
- Rice — about 28g carbs per 100g (cooked). Easy to digest.
- Bread — wholemeal for training days, white for pre-race (easier to digest). About 40g carbs per 100g.
- Potatoes — about 17g carbs per 100g. Baked potatoes are underrated marathon fuel.
- Bananas — about 23g carbs each. The perfect mid-morning snack during training blocks.
Protein for Recovery
Don’t neglect protein during marathon training. Aim for 1.4-1.7g per kilogram of body weight per day (about 100-120g for a 70kg runner). Protein repairs the muscle damage from long runs and helps you recover between sessions.
Good sources:
- Chicken breast — about 31g protein per 100g
- Greek yoghurt — about 10g protein per 100g (Fage is widely available in Tesco and Sainsbury’s)
- Eggs — about 6g each. Two eggs on toast is a solid post-run breakfast.
- Tinned tuna — about 25g per tin. Quick and cheap.
Practice Your Race Fuel
From 8 weeks out, use every long run to practise your race-day nutrition. Try different gels, chews, and drinks during training to find what works for your stomach. Some people can handle thick, sticky gels. Others need them with water. Some can’t tolerate them at all and do better with Jelly Babies or wine gums. Find out now, not at mile 15.
4 Weeks Out: Fine-Tuning
Your mileage is peaking and tapering starts soon. Nutrition becomes more precise.
Dial In Your Race-Day Plan
By this point, you should know:
- Which gel brand works for you (SiS, Maurten, HIGH5, and Torq are the most popular in UK running shops)
- How many gels per hour you can tolerate (typically one every 20-30 minutes)
- Whether you need water with your gels or can take them dry
- What you’ll eat for breakfast on race morning
Hydration Baseline
Start paying attention to your hydration. Most UK runners don’t drink enough during training. Aim for 2-3 litres of water daily, plus whatever you lose during training. If your urine is consistently pale straw-coloured, you’re fine. Dark yellow means you’re behind.
Reduce Fibre Gradually
In the final 2-3 weeks before the race, gradually reduce high-fibre foods. Your gut needs to be calm on race day, and the high-fibre wholemeal bread and brown rice that’s great for training can cause GI distress during the race. Switch to white bread, white rice, and low-fibre cereals.
Race Week: The Carb Load
This is the most misunderstood part of marathon nutrition. Carb loading doesn’t mean eating mountains of pasta the night before.
How Carb Loading Actually Works
Proper carb loading is a 3-day process in the final 72 hours before the race. You increase your carbohydrate intake to 8-12g per kilogram of body weight while reducing training. For a 70kg runner, that’s 560-840g of carbs per day — a substantial amount.
What 600g of Carbs Looks Like
A realistic day during carb loading:
- Breakfast: large bowl of porridge with banana and honey, 2 slices white toast with jam (about 120g carbs)
- Mid-morning: 2 rice cakes with peanut butter, sports drink (about 60g carbs)
- Lunch: large portion of white pasta with tomato sauce, bread roll (about 130g carbs)
- Afternoon snack: bagel with honey, banana (about 80g carbs)
- Dinner: chicken stir-fry with large rice portion, naan bread (about 140g carbs)
- Evening: bowl of cereal, toast with jam (about 80g carbs)
That gets you to roughly 610g. It feels like a lot of food, and your weight will go up 1-2kg from the water that’s stored alongside glycogen. This is normal and desirable — it’s fuel, not fat.
The Night Before
Eat your main carb meal at lunchtime on the day before the race, not at dinner. This gives your body more time to digest and store the glycogen. Dinner should be a normal-sized meal — familiar, carb-based, low fibre. Pasta with a simple tomato sauce is the classic for a reason. Nothing spicy, nothing you haven’t eaten before.
Race Morning: The Pre-Race Meal
Get this wrong and you’ll spend the first five miles with a stitch or worse.
Timing
Eat 2.5-3 hours before the start. For a 9am marathon start (common at London, Manchester, Edinburgh), that means eating at 6am. Set an alarm.
What to Eat
Your breakfast should be:
- Familiar — you’ve practised this during training, it doesn’t upset your stomach
- Carb-heavy — about 1-2g carbs per kilogram of body weight (70-140g for a 70kg runner)
- Low fibre, low fat — easy to digest
- Low protein — protein slows digestion
Classic options:
- Porridge with honey and banana — the UK runner’s go-to for good reason
- White toast with jam or honey — simple and effective
- Bagel with peanut butter and banana — slightly heavier but works for some
- Energy bar and a banana — if you can’t face “real” food at 6am
Pre-Race Sipping
From breakfast until the start, sip water or a sports drink (about 400-500ml total). Don’t chug a litre at the start line — you’ll need the toilet by mile 2.
During the Marathon: What to Eat and When
This is where your training-block practice pays off.
The Fuelling Schedule
Here’s a framework that works for most runners:
- Miles 1-5: nothing. You’re running on breakfast and glycogen. Focus on settling into pace.
- Mile 5-6: first gel or fuel. Your stomach is calm, the race adrenaline has settled.
- Every 4-5 miles after that: another gel or equivalent carb source (about every 20-30 minutes).
- Mile 20-22: this is where fuelling matters most. Don’t skip this one — even if your stomach is protesting, get something in.
- Mile 22+: if you’ve fuelled well, you won’t need much more. A last gel at mile 22-23 is insurance.
What to Use
- Energy gels — most popular. SiS Go Isotonic (don’t need water), Maurten Gel 100, HIGH5 Energy Gel. About £1-2 each, buy in bulk before the race.
- Energy chews — Clif Bloks, SiS Energy Chews. Easier on some stomachs, take longer to eat.
- Real food — Jelly Babies (roughly 5g carbs each), dried dates, wine gums. Cheaper and can taste better at mile 18 when everything sweet makes you gag. Many UK marathons hand them out at aid stations.
- Sports drinks — Lucozade Sport, SiS Go Electrolyte. Available at most UK marathon water stations. These provide both carbs and fluid.
The Golden Rule
Nothing new on race day. Every gel, chew, drink, and snack should be something you’ve tested during training. Your digestive system under race stress is not the time for experiments.
Hydration Strategy
Dehydration slows you down. Over-hydration (hyponatraemia) is dangerous. The sweet spot is somewhere in between.
How Much to Drink
Aim for 400-800ml per hour, depending on temperature, your sweat rate, and body weight. In a typical UK spring marathon (8-14°C), most runners need about 400-600ml per hour. In a warm one (18°C+), closer to 800ml.
When to Drink
UK marathons place water stations every 3-5 miles. Take a cup at most stations, but you don’t need to drink the entire cup. A few mouthfuls per station keeps you topped up without sloshing around uncomfortably.
Water vs Electrolyte Drink
If you’re fuelling with gels (which provide carbs), water is fine at most stations. Switch to the electrolyte drink at one or two stations to replace sodium, especially in warm weather. If you’re using a running hydration vest, you can carry your own fluid and sip consistently rather than gulping at stations.
Signs of Dehydration
- Dark urine at a portaloo stop (early sign)
- Headache
- Dizziness
- Significant thirst (by this point, you’re already behind on fluids)
Post-Marathon Recovery Nutrition
You’ve crossed the line. Now feed the recovery.
The First 30 Minutes
Your muscles are most receptive to glycogen replenishment in the first 30-60 minutes after finishing. Eat a combination of carbs and protein — the classic 3:1 or 4:1 ratio.
Options:
- Recovery shake — if you can stomach it. SiS REGO or HIGH5 Recovery are popular at UK events.
- Chocolate milk — surprisingly effective. The carb-to-protein ratio is nearly perfect for recovery.
- Banana and a handful of nuts — whole food option.
- Whatever the finish line provides — most UK marathons offer bananas, chocolate, energy bars, and water. Eat what you can.
The Rest of the Day
Eat a proper meal within 2-3 hours of finishing. You’ve burned 2,500-3,500 calories, and your body needs to replenish glycogen, repair muscle, and rehydrate. This is not the day to calorie-count.
Good recovery meals:
- Chicken pasta with vegetables — carbs, protein, micronutrients
- Sunday roast — seriously, the potatoes, meat, and veg cover everything
- Pizza — you’ve earned it, and the carb-protein-fat combination is recovery-appropriate
Rehydration
You’ll be dehydrated even if you drank well during the race. Aim to drink 1.5 litres for every kilogram of body weight you lost during the race. Weigh yourself before and after if you want to be precise. Most runners need 2-3 litres of fluid in the hours after finishing.
Common Nutrition Mistakes
These are the ones I see at every UK marathon, and the ones that ruined my own early races.
Trying New Food on Race Day
Worth repeating because it’s the most common mistake. That gel the person next to you is using might be brilliant — or it might send you sprinting for the portaloos at mile 8. Test everything during training.
Skipping Breakfast
“I’ll feel heavy” — you’ll feel a lot heavier at mile 15 without breakfast glycogen. Even if you can’t face a full meal, eat something. A banana and a slice of toast is enough.
Not Eating Early Enough During the Race
Many first-time marathoners wait until they’re hungry to eat. By then, you’re already depleted. Start fuelling at mile 5-6 whether you feel you need it or not. Prevention is easier than rescue.
Drinking Too Much
Hyponatraemia (dangerously low sodium from excessive water intake) is rare but serious. Don’t force yourself to drink more than you need. Drink to thirst, and use electrolytes in warm conditions. The NHS advises listening to your body rather than following rigid hydration rules.
Carb Loading = Overeating
Carb loading means increasing the percentage of carbs in your diet, not just eating more food overall. If you add 800g of pasta on top of your normal diet, you’ll feel bloated and sluggish. Replace protein and fat calories with carb calories to increase total carb intake without inflating total calories.
Frequently Asked Questions
How many gels do I need for a marathon? Most runners need 4-7 gels during a marathon, depending on pace and personal tolerance. Start at mile 5-6 and take one every 20-30 minutes. A 4-hour marathon runner might use 5-6 gels. Test your exact number during long training runs.
When should I start carb loading for a marathon? Begin 3 days before the race (72 hours out). Increase carbohydrate intake to 8-12g per kilogram of body weight while reducing training. This tops up your glycogen stores beyond normal levels and provides the fuel to get through 26.2 miles.
What should I eat on marathon morning? A familiar, carb-heavy, low-fibre breakfast 2.5-3 hours before the start. Porridge with honey and banana is the UK classic. Aim for 1-2g of carbs per kilogram of body weight. The key rule: nothing you haven’t eaten before a long training run.
Can I run a marathon without gels? Yes. Many runners use Jelly Babies, dried dates, wine gums, or sports drinks instead. The important thing is getting 30-60g of carbohydrate per hour after the first hour of running. How you deliver those carbs is personal preference.
How much water should I drink during a marathon? About 400-800ml per hour depending on temperature and your sweat rate. In a typical UK spring marathon, 400-600ml per hour is sufficient. Take a few mouthfuls at each water station rather than drinking full cups at every stop.