How to Fuel a Marathon: The Complete No-BS Guide

Everything you actually need to know. Nothing you don't.

You have done the training. The long runs, the intervals, the early mornings, the tired legs. You have put months of work into getting to the start line.

And then you eat the wrong thing at kilometre 25 and watch your race fall apart.

Nutrition is the part of marathon performance that most athletes underprepare for. Not because they don't care. Because there is so much conflicting information out there that it is hard to know what to actually do.

This is the guide we wish existed when we started. No product pitching, no filler. Just the science, the numbers, and a practical plan you can actually execute on race day.

Start Here: The Three Things That Actually Matter

Every credible sports scientist working in endurance nutrition will tell you the same thing. On race day, three variables drive your performance outcome more than anything else.

Carbohydrates. Sodium. Fluid.

Get those three right and you give yourself the best possible shot at running your race. Get them wrong and it doesn't matter how fit you are. The wall will find you.

Let's go through each one.

Carbohydrates: Your Engine Fuel

Your muscles run on glycogen. That is just carbohydrate stored in your muscle tissue and liver. The problem is your storage is limited. Even a well-fuelled athlete only carries enough to last roughly 90 minutes at race pace before those stores start running low.

A marathon takes longer than 90 minutes. So you need to be taking carbohydrates in from the outside, consistently, from early in the race.

Research tracking marathon runners across a full race found that athletes who met the recommended carbohydrate intake of 60 to 90 grams per hour during competition were significantly more likely to finish under three hours compared to those who didn't. Maurten

That is a meaningful finding. Not just that carbs help. That hitting the right number separates the athletes who run the race they trained for from the ones who survive the back half.

Despite this evidence, the average measured carbohydrate intake of marathon runners during racing sits at only around 35 grams per hour — less than half the upper recommended amount. Endurance

Most athletes are leaving performance on the table. Not because they can't absorb more. Because their fuel causes GI problems before they get the chance.

This is where the type of carbohydrate matters as much as the amount. Glucose and fructose use different absorption pathways in your gut. Combining them lets you absorb significantly more total carbohydrate per hour without overloading either system. That is the science behind 2THRV's formulation: organic maple syrup for glucose delivery, organic dates for fructose through a second absorption lane, working simultaneously so more fuel actually reaches your muscles.

The target: 60 grams per hour for efforts under three hours. Up to 90 grams per hour for longer efforts or hotter conditions.

Sodium: The One Athletes Consistently Get Wrong

Research shows that sodium intake during marathons averages only around 192 milligrams per hour — significantly lower than the 270 to 300 milligrams per hour recorded in triathletes and trail runners doing comparable efforts. Maurten

Most marathon runners are not replacing anywhere near the sodium they are losing through sweat. And that matters more than most athletes realise.

Sodium is not just about avoiding cramps, though it helps with that too. It regulates fluid balance. It tells your body to hold onto the water you are drinking rather than flushing it out. Without adequate sodium, you can drink plenty of fluid and still end up dehydrated at a cellular level.

Sports nutrition research recommends sodium intake of between 500 and 1500 milligrams per hour during endurance racing, with the exact amount depending on individual sweat rate and conditions. Drinking water alone without electrolytes increases the risk of hyponatremia, where sodium levels in the blood drop dangerously low. Scientific Triathlon

The mineral salt in 2THRV contributes to your sodium intake with every pouch. But for longer efforts and hot race days, you will also want an electrolyte drink alongside your gels rather than plain water.

The target: 500 to 1000 milligrams of sodium per hour in standard conditions. More in heat. Match your fluid intake with electrolytes, not just water.

Fluid: Simpler Than You Think

The research on hydration has shifted in recent years. The old advice to drink as much as possible has been replaced with something more practical and more effective.

Drink to thirst.

Current research supports drinking to thirst as the most reliable hydration strategy for endurance athletes, preventing both dehydration and the more dangerous condition of hyponatremia, where excess water intake dilutes sodium levels in the blood and can cause symptoms ranging from nausea and headache to seizures in severe cases. The Feed

Your body is a remarkably good thirst regulator during exercise. Trust it. Sip consistently rather than gulping at aid stations. And always pair your fluid with electrolytes so what you drink actually stays where it needs to be.

The target: drink when you are thirsty. Aim for roughly 400 to 600 millilitres per hour in mild conditions. More in heat. Always with electrolytes.

The Race Day Timing Plan

Here is how to put it all together practically.

Two days out: Start increasing your carbohydrate intake significantly. Research supports targeting 8 to 12 grams of carbohydrate per kilogram of bodyweight per day for the 36 to 48 hours before the race. Nutritiontriathlon For a 70kg runner that is 560 to 840 grams of carbohydrate daily. Reduce fat and fibre during this window to minimise digestive stress on race morning.

Race morning: Eat a familiar, carbohydrate-rich meal around three hours before your start. A smaller carbohydrate-rich snack around 30 to 60 minutes before the race tops up your glycogen without sitting heavily in your stomach. Scientific Triathlon Keep it simple. Race morning is not the time to experiment.

First 30 minutes: Start fuelling earlier than feels necessary. Most athletes wait until they feel hungry or low on energy. By that point you are already behind. Take your first gel within 30 minutes of starting regardless of how you feel.

Every 30 to 45 minutes after that: Take a gel consistently throughout the race. Do not wait for hunger. Do not skip one because your stomach feels off. Consistency is the whole game.

Aid stations: Take fluid at every station. Small sips. Do not gulp. Pair with electrolytes where available.

The back half: This is where the race is won or lost. Research from ultra-endurance events shows that athletes who finish strong consume consistently more calories per hour than those who slow down or drop out, with successful runners maintaining above 250 calories per hour while struggling athletes average below 200. Maurten Stay on your fuelling plan even when it feels hard to eat. Especially then.

What to Actually Use

This is where most fuelling guides get uncomfortable, because most of them are written by brands selling their own product.

We will be straight with you. We think 2THRV is the best gel on the market, and here is why that matters for your marathon plan specifically.

The most common reason athletes fall short of their 60 to 90 gram per hour target is gut distress. Synthetic ingredients, maltodextrin, artificial flavours, and preservatives put extra stress on a digestive system already working under reduced blood flow and mechanical impact.

2THRV is made from five whole food ingredients your gut recognises and processes efficiently. Organic maple syrup and organic dates provide the glucose and fructose combination the research identifies as optimal. Mineral salt supports your sodium target. And nothing in the formula asks your gut to do extra work it doesn't need to do.

One pouch delivers approximately 30 grams of carbohydrate. Two per hour puts you squarely in the research-backed sweet spot.

The Short Version

Train your nutrition like you train your legs. Start fuelling early. Hit 60 to 90 grams of carbohydrate per hour. Replace sodium consistently. Drink to thirst with electrolytes, not just water. And choose fuel your gut can actually handle under race conditions.

The wall is not inevitable. It is a fuelling failure. And fuelling failures are solvable.

Go run your race.

[Try 2THRV — whole food endurance fuel built for race day.]

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