What to Eat Before a Marathon: The No-Nonsense Guide to Fuelling Up Without Blowing Up

It’s 5:30am on race morning. The alarm has gone off. It’s doing that thing where it’s not quite raining but the sky is doing its best impression of a wet flannel. You’ve got your vest laid out, your trainers laced (twice, for luck), and a very important question hanging over you like a fluorescent cloud: what to eat before a marathon without spending miles 18 to 26 sprinting for a Portaloo?

Good news: this is entirely preventable. Bad news: a lot of runners get it wrong. Not because they’re careless. Because the advice out there is either too vague (“eat carbs!”) or so sciency it requires a nutrition degree to decode. So let’s cut through it. Here’s what actually works – from the three days before the gun fires, right down to what you’re shovelling in before you lace up.

Why What You Eat Before a Marathon Matters More Than You Think

Your muscles store energy as glycogen. You’ve got roughly 90 minutes of hard running in the tank before those stores start to run dry. A marathon – unless you’re Kipchoge, and let’s be honest, you’re not – takes considerably longer than 90 minutes. The London Marathon median finish time sits around 4 hours 40 minutes for men and just over 5 hours for women. That’s a long time to run on fumes.

The solution isn’t to eat a massive pasta dinner the night before and call it done. That’s one of the most persistent myths in amateur running. Real carb loading is a multi-day process. And doing it right can be the difference between a strong finish and a death march through mile 22 while a man in a rhino costume overtakes you.

Carb Loading: Start Early, Not the Night Before

Here’s where most club runners go wrong. They taper their training brilliantly (or obsessively Google their symptoms for two weeks – either/or). But they leave all their carb loading to one big bowl of pasta on Saturday night before a Sunday race. That’s not carb loading. That’s just a big dinner followed by a dodgy night’s sleep and possibly some bloating you really don’t want at mile 3.

Proper carb loading starts two to three days out from race day. The goal is to top up your muscle glycogen stores fully, which takes time. You can’t rush it. Your muscles absorb carbohydrate gradually, and cramming it all in at once mostly just makes you feel heavy and gassy. Neither of which is ideal at a 7am start in front of several thousand strangers.

How Many Carbs Do You Actually Need?

This is where the numbers get useful. Runner’s World and sports nutrition bodies broadly recommend aiming for 8 to 12 grams of carbohydrate per kilogram of bodyweight per day during the two to three days of carb loading before a marathon. So if you weigh 70kg, you’re looking at 560g to 840g of carbs per day. That’s a lot of pasta. More than you’d normally eat. Which is the point.

For most runners, aiming for the lower end of that range (around 8g per kg) is more realistic and less likely to leave you feeling like an overstuffed sofa cushion on race morning. The NHS Sport and Exercise Nutrition guidelines back a similar approach for endurance athletes.

Good carb sources to lean on during this window:

• White rice and pasta (lower fibre = less gut drama, which you’ll thank yourself for later)
• Potatoes and sweet potatoes (baked, not fried – this isn’t a chippy run)
• White bread, bagels, and rolls
• Porridge and breakfast cereals
• Bananas and other fruit
• Rice cakes and crackers
• Energy bars and sports drinks (in moderation – real food first)

Also: cut the fibre down in these final days. High-fibre foods are brilliant for your health and your Sunday long run, but right before a marathon they’re a liability. Switch from brown rice to white. Ease off the brassicas and legumes. Your stomach – and every runner near you on the start line – will be grateful.

The Three Days Before: A Rough Game Plan

You don’t need to be obsessive about this. Obsessiveness during taper is already covered (see our piece on surviving marathon taper madness). But a rough framework helps.

Three days out: Start nudging carb intake up. Add an extra portion of rice or pasta at lunch and dinner. Keep protein and fat moderate. Drink plenty of water and consider adding a pinch of salt or an electrolyte tab to one of your drinks – your muscles need sodium to store glycogen efficiently.

Two days out: Carb intake goes up again. Keep meals familiar. This is not the time to try the new Thai place your mate’s been raving about, or to let your partner cook that experimental lentil dish they’ve been saving. Familiar food only. Low fibre. Keep hydrating.

The day before: Same approach. Spread your carbs across the whole day rather than loading them all into dinner. Eat your last substantial meal at a reasonable time – early evening at the latest. Give your gut a fighting chance to sort itself out before you go to bed. Sleep in your kit if you have to. No shame. We’ve all been there.

Race Morning: What to Eat Before a Marathon When Your Stomach Is Already Nervous

Your stomach on race morning is doing approximately seventeen things at once. It doesn’t need you throwing a full English at it. Keep it simple, keep it familiar, and give yourself time to digest.

Aim to eat two to three hours before the start. Most sports nutritionists recommend around 1 to 4g of carbohydrate per kg of bodyweight in this window – again, toward the lower end if your stomach tends to misbehave. That means around 70 to 140g of carbs if you weigh 70kg.

Classic race morning breakfasts that actually work:

• Porridge with a banana and a drizzle of honey
• White toast with peanut butter and jam (yes, jam counts as carbs – take the win)
• Bagel with cream cheese or peanut butter
• Rice cakes with banana
• A bowl of cornflakes or Weetabix with semi-skimmed milk

Whatever you choose: you must have tested this in training. Not the morning of a big race. Use your long runs to trial your race morning breakfast. Run a few 18-milers off the same meal. If your stomach handles it fine at mile 15, you’re good. If it doesn’t, adjust before race day – not on it.

One small top-up trick: a gel or banana about 20 to 30 minutes before the start can give you a useful spike in blood sugar. Especially helpful if you’re doing a longer race and the start corrals have you standing around in the cold for an hour. Just make sure it’s a gel you’ve trained with. New gels on race day is how you end up becoming a cautionary tale on a running forum.

For a deeper look at fuelling once the race is actually underway, our guide on fuelling during a marathon covers everything from gel timing to avoiding the wall at mile 20.

What to Avoid in the Days Before a Marathon

As important as what you eat is what you don’t eat. A few things to steer well clear of in the final 48 to 72 hours:

• High-fibre foods: Lentils, baked beans, broccoli, cabbage, whole grains in large quantities. Goodbye for now.
• Spicy food: Tempting? Yes. Wise? Absolutely not.
• Alcohol: It dehydrates you and interferes with glycogen storage. The celebration pint can wait until after the finish line medal photo.
• Anything new: This applies to food, supplements, gels, drinks – anything you haven’t used in training. Your gut is not a laboratory.
• Huge portions at one sitting: Spread your carbs across the day. Your digestive system will thank you at mile 6.

Real Talk

Right. Here’s the summary. Carb loading works – but it takes two to three days, not one pasta dinner. Aim for around 8 to 10g of carbs per kilogram of bodyweight per day in that window, keep fibre low, eat familiar food, and don’t experiment with anything new. On race morning, eat two to three hours before the start – something plain, carb-heavy, and (crucially) something you’ve tested on a long run. A top-up gel 20 to 30 minutes before the gun doesn’t hurt either.

It’s not complicated. It just requires a bit of planning and the willpower to say no to the vindaloo on Friday night. You’ve run 20-milers in the dark in January. You’ve survived 5am rain alarms and black toenails and the indignity of intervals in a howling crosswind. You can eat plain pasta for three days.

Good luck. Trust your training. And for everything that happens once the gun fires, go and read our full guide on fuelling a marathon from start to finish – it’ll save your legs at mile 20.