Race Day Fuel. What to Eat Before a Marathon


A healthy diet is a vital part of any running regimen.

Not only does it affect how you feel on a day-to-day level, but it’s absolutely critical to your performance.

But…you already knew that.  Any runner worth his or her salt knows that a healthy diet is a bare minimum requirement for anyone who takes the sport even remotely seriously.

What a lot of runners DON’T know, however, is how this changes when it comes to fuelling up for a big event.  

And it’s understandable - trying to figure all the nitty gritty dietary details that go into preparing for something as gruelling as a marathon can be daunting, to say the least. 

In today’s article, we’re going to clear all of this up for you aspiring marathoners.  We’ll be talking not only about what to eat on the day of a big race, but how to handle the days leading up to it, what you should eat - and why a lot of the popular advice floating around out there should be taken with a pinch of salt.


How Most People Screw It Up

warm up


Almost any athlete (endurance or otherwise) messes this up at some point in their career…and almost all of them do it the exact same way - by eating WAY too much food.

This usually happens to the best of us early on.  Maybe it was a high school coach who told you to eat a big bowl of pasta the night before a competition. 

Makes sense, right?  Pasta=carbs=energy=better performance.  The problem is that most inexperienced trainees have a tendency to blow it way out of proportion.  

Following the assumption that “more is better”, they tend to take the “pre-day carb fill” and run with it - cereal, Gatorade, crackers, donuts (no carb is safe). 

Now, think about how this turned out for you…yeah, thought so.  Rather than increase your performance, it actually had the complete OPPOSITE effect.  

Most of us will wake up the morning after gorging ourselves on 7000 calories feeling bloated and groggy- definitely not optimal for anything besides laying on the coach.

And while almost everyone who tries this learns their lesson, the fact is that most endurance athletes still eat far too much food when preparing for an event. 


The Problem With “Carb Loading”

carb loading


Let’s get one thing out of the way - carbohydrates are an essential part of any marathoners diet.  

In fact, they’re an essential part of everyone’s diet period.  As your body’s preferred fuel source, carbs are responsible for supplying you with the energy you need to go about your daily life.

As a runner, however, they’re particularly important as a source of fast, readily-available energy, and learning how to master your carb intake is an essential skill for anyone planning to compete.

The problem is that most people have a fundamental misunderstanding about how the process works.

“Carb loading” refers to loading up on carbohydrates during the days and hours before any kind of big sporting event.

It works like this - carbs breakdown into glucose, and glucose is converted into glycogen for fuel.  This glycogen is then stored in the liver and muscles for future use.

And since endurance work requires quite a bit of glycogen, it makes sense that athletes would want to raise their levels pre-competition (particularly in the muscles) as much as humanly possible.


Common Misconceptions



One of the big misunderstandings, however, comes from athletes who have an inflated sense of what this can actually do for them.

In fact, most people who think they need to “carb load”, don’t.  Most sports simply aren’t performed for long enough to warrant any carbohydrates beyond what would be consumed as part of a “normal” diet.

While the numbers vary, you can generally expect a good 1.5 to 2 hours of continuous, moderately high activity before you start to run out of gas.  

And since the majority of sports don’t require participants to perform anything close to that, jacking your carb levels through the roof the day before a basketball game doesn’t really make much sense. 

The majority of these competitors would simply be better off eating their normal, reasonably high carb diet.

Now, as runners, we’re in a slightly different situation than most people given the duration of our sport.  

For a full marathon, even ELITE runners will find themselves clocking in over 2 hours.  A fairly decent runner is looking at least 4 hours, while those who are less experienced could find themselves running for as long as 8 WHOLE HOURS.

Even if you’re running a half marathon, chances are you’ll find yourself running on fumes at some point during the race.

So, now that we’ve established why distance runners are one of the few athletes who should actually be carb loading, let’s talk about the second problem with this whole concept - misunderstanding and overestimating the size of your “gas tank”.  

This mistake comes form assuming that your body has unlimited room to store all this extra glucose and glycogen.  That’s why every “newbie” attempts to cram 1000’s upon 1000’s of extra calories into their system - they think that it can all be used on the “big day” to give them an extra edge.

Unfortunately, it’s not that simple.  Apart from the liver, the only reliable place for your body to hold excess glycogen that can be released during exercise for fuel is in your muscles (hence the term “muscle glycogen”).

In reality, most of those extra carb calories you’ve inhaled are either still being digested, or are being stored as body fat.


How Many Carbohydrates Should You Be Eating?

race day carbs


Hopefully by now you’ve figured out that carb loading isn’t quite as simple as you thought.  So…how much should you be eating before the big race?

The exact amount is going to depend on a number of factors, including your weight and level of fitness, and will require some experimentation.

With that said, most runners will find that around 12-16 grams of carbs per kilogram of body weight in the 48 hours or so leading up to a race is plenty.

This means that a 60 kilogram woman will require 720-960 grams of carbs, while a 75 kilogram male will require about 900-1200.

To put that in perspective, 100 grams of (uncooked) pasta contains a little over 75 grams of carbs, while a single sweet potato has about 25 grams.

If you come from the “more is better” school of thought, this might not seem like a lot when spread out over two days.  But trust us - it’s PLENTY.  Not only is it unnecessary to be consuming more, but it can even be detrimental if the additional food intake causes you to feel sluggish.


Understanding The Role Of Protein

good protein


Now that we’ve broken down the role that carbs play in your diet, let’s talk about the other two macronutrients - fat and protein.

And when it comes to pre-race nutrition, protein is definitely something you should be focused on.

Really, it’s something you should be focused on most of the time.  A lot of runners are still under the misguided belief that protein is just for bodybuilders and strength competitors.

In reality, nothing could be further from the truth.  

As an athlete, you should be eating more protein than the average person.  While the exact number will vary between runners, generally speaking you should aim for at least 1-1.6 grams per kilogram of body weight per day.

So, if you weigh in at 60 kilograms, you should aim for anywhere from 60-96 grams of protein per day as a general dietary rule.

The reason that runners need more of this macronutrient is simple - protein is responsible for maintaining existing muscle, as well as creating new muscle.  It’s also critical for maintaining strong bones, and for helping the body recover after intense exercise.

And while you may not realize it, every time your foot strikes the ground during a run, you’re generating the equivalent of anywhere from 2 to 7 times your body weight.  Over time, this impact can SERIOUSLY add up, and if you aren’t getting enough protein in your diet, you’re going to have a hard time recovering.

But how does this apply to your pre-race diet?  Should you be increasing your protein as well as your carbs?

Generally speaking - no.  While protein is important, as long as your REGULAR diet contains a sufficient amount, increasing your carbs should be priority.  Keep your intake as usual and you should be fine. 

You will, however, want to consume more protein than normal AFTER the race, since…well, since running for 42 kilometres non-stop isn’t exactly something your body is used to recovering from.


What About Fat?

bad fats


Fat gets a bad rap, but consuming enough of it is important for a number of bodily functions.  These include hormonal maintenance and cell function, as well as providing a layer of protection for your organs.

But fats can also be used as fuel in the absence of carbs and glucose.  This is why many low carb diets make up the difference with dietary fat - to provide an alternative source of energy. 

While some people may prefer low carb diets, for athletes (and in particular endurance athletes), this is far from an optimal strategy.  As a fuel source, fat tends to work a lot better at lower intensity levels - and since running is a fairly high intensity activity, it just simply is not as efficient as carbs when it comes to providing energy.

For this reason, you’ll want to keep your fat intake relatively low leading up to the race.  Obviously you shouldn’t eliminate it completely, but it should come in last in terms of prioritization.



What To Eat During The Days Before The Race

Now that we’ve covered the basics, let’s talk about exactly what you should be putting in your mouth to make sure you perform your best on race day. 

As we mentioned previously, you’ll want to start your pre-race diet about 48 hours prior to the event, aiming for about 12-16 grams of carbs per kilogram of bodyweight over a two day period.  That will give you enough time to get all the extra glycogen you’ll need without having to force feed yourself.

Pro tip - if your race is on a Saturday, go hard on the carbs Thursday, but pull back a bit on Friday.  The reason for this is the fact that eating more than usual can affect your sleep, and you want to make sure that you’re getting the best sleep possible before the race.

As for carb sources, go with simple carbs that are easy to digest- pasta, bread, bananas, tortillas, juice and white rice are all good choices.  In most cases, complex carbohydrates with fibre are a healthier choice, but for the purpose of preparing for a race, you actual want to avoid this, since all the extra fibre can bloat your stomach.

During this time, you should also avoid pairing your carbs with any fatty or greasy food (think spaghetti and plain tomato sauce rather than Pizza Hut) and try to get your protein from lean sources like chicken, turkey and egg whites.


What To Eat On Race Day

race day fuel


With your carb loading finished and out of the way, the morning of a big race is all about NOT screwing it up.  That means eating a relatively small, high carb, moderate protein meal that you know will “agree” with your stomach.

Basically, whatever you USUALLY eat before a run is what you should be eating now (today isn’t the day to start experimenting).

Again, simple, easy-to-digest carbs like bananas, white bread, cereal or bagels and a bit of lean protein should do the trick.  Try to consume this meal at least a few hours before the start of the race to allow for proper digestion.

You should also try to avoid consuming dairy, since many people find that it gives them issues with bloating and congestion that you’ll want to avoid.

Preparing for a marathon is stressful - but that doesn’t mean it needs to be complicated.  Get your food timing right, take in adequate carbs, and (for the love of God) don’t stuff your face, and you’ll show up on race day a well-fuelled machine.




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Sam MurrayAbout the author

Samantha is the content creator and co-founder of RevereSport. Through her passion for fitness, nutrition and active travel, she aims to inspire others to lead healthier, sustainable lifestyles without compromising on fun.

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