What is Carb Loading? Why Do Long Distance Runners do this?

What do you do before going on a long road trip? Of course, you’d top up your gas tank first, making sure that it’s full all the way to the top. Long-distance runners also do something similar the night before a big race, but they call it carb-loading.

Instead of filling gas in a tank, carb-loading involves eating large amounts of carbohydrates to supply themselves with enough energy to last the entire run.

But carb-loading isn’t as simple as eating a bowl of pasta. That’s why in this article, we’re going to explore everything you need to know about carb-loading so that you can reap its benefits the next time you go on a long-distance run.

What Is Carb Loading?

Let’s start with the most basic question: What is carb loading and why do long-distance runners do this?

Simply put, carb-loading is a nutritional strategy where you eat lots of carb-rich foods before an endurance activity lasting hours.

Long-distance runners typically use this strategy because it allows them to sustain a run for hours on end without getting exhausted too soon.

But carb loading isn’t just about sitting down and eating until you’re full. Remember: it’s a strategy, which means there are many finer details that go into it.

As we’ll explore in the rest of this article, it’s crucial to understand what carb-loading does to the body before you start doing it. That will enable you to eat carbohydrates from the best sources, in the correct amounts, and only at the ideal times.


Effects Of Carbohydrate Loading On Runners

Carbo-loading doesn’t work for all athletes, like those who rely on short bursts of intense energy. However, they work exceptionally well for runners and other endurance athletes. That’s because these sports demand a sustained supply of energy from the athlete’s bodies, or else they’ll experience fatigue that’ll slow them down.

Carb-loading enhances a runner’s stamina, allowing them to continue going for much longer before using up all their energy. Since exhaustion is basically delayed thanks to the carb-loading, runners can cover more distance and complete their runs more efficiently.

How Does Carb-loading Work?

Firstly, it’s essential to understand the science behind carb-loading. You see, the human body uses carbohydrates to generate energy. Whenever our bodies digest carbs, they get converted into glycogen that’s stored in our muscles and the liver.

When we’re in a situation that demands lots of energy, like running long-distance, our bodies burn up that glycogen to keep us going.

The problem with long-distance running is that it goes on for so long that those glycogen stores finish entirely. Runners call that ‘hitting the wall’ when they’re hit with exhaustion somewhere during their run. And no matter how well you train, you’ll eventually run out of glycogen on a long-distance run.

The point of carb-loading is to maximize or exceed our glycogen stores and delay hitting the wall as much as possible. Of course, everybody’s body reacts differently to carb-loading. That’s why it’s crucial to find a carb-loading strategy that works well for you.

What Does Carb-Loading Look Like?

Carb-loading can take many different forms, with some approaches being more complicated than others. Some long-distance runners might keep it simple with a one-day carb-load, or they might prefer a three- or six-day program instead.

Let’s explore what that might look like:

One-Day Carb-Loading

This is the most straightforward carb-loading approach of all. Basically, you spend the whole day before your race consuming a high-carbohydrate diet without doing any exercise.

With this approach, the rule of thumb is to consume 4.5 grams of carbohydrates per pound of your bodyweight.

You shouldn’t do any physical training while carb-loading this way, since your aim is to keep your glycogen stores as full as possible for race day.

Three-Day Carb-Loading

Even this approach comes in many different variations. But basically, they involve intensive training on the first day to deplete your body’s glycogen stores in its muscles and liver.

Then, you spend the next two days consuming a high-carbohydrate diet without any exercise at all.

The idea is simple: use up all the glycogen has on the first day with exercise, then spend the next two days rebuilding those stores.

Six-Day Carb-Loading

If you’re looking for a more sophisticated approach, then the six-day carb-loading program might be for you. For the first three days, you only consume a moderate amount of carbohydrates, before you start eating much more for the next three days.

Throughout the entire program, your exercise will decrease. You can train somewhat regularly in the first two days, but from that point on, you’re training less and less to preserve the glycogen building up in your muscles. It’s possible that you may retain some extra weight prior to your race. Don’t worry when you run your race you will have depleted your glycogen stores and lost the extra weight.

Carb-loading Based on Weight

Based on 4.5 grams per pound of body weight (10 grams per kilogram of body weight) Source: Mayo Clinic.
For a sample carbohydrate-loading meal plan click Mayo Clinic.
PoundsKilogramsTotal Carbs (grams)

Common Carb-Loading Mistakes

Remember: carb-loading isn’t about eating as much as your favorite foods just because you can. It’s a nutritional strategy, so you need to do it the correct way to enjoy the benefits it offers.

Here are some of the most common carb-loading mistakes that people make.

Doing It Unnecessarily

Some people, especially those who are new to running, might engage in carb-loading even when it’s not necessary. Remember: your body only benefits from carb-loading if you’re running for more than 90 minutes.

So, doing this is unnecessary if you’re running for shorter periods of time. That’s also true if you’re engaging in sports that require short bursts of energy, like weight lifting or sprinting.

Training Excessively

The whole point of carb-loading is to maximize the glycogen stores in your body. Training excessively during this period will only undo all your hard work!

Overeating Fat

It’s called a ‘carb-load’, not a ‘fat-load’! Fats are dense in calories, so when you eat foods that are both high in carbs and fat, you’ll probably exceed your daily maximum of calories.

To avoid this, stick to foods that are high in carbs but not that high in fat.

Overeating Fiber

Fiber is also something that people tend to consume while carb-loading. Excessive fiber can cause you stomach discomfort, and that’s not something you want to feel on race day.

You want to focus on running your course, not running to the closest bathroom.

Miscalculating Your Carb Needs

This is worth saying again: carb-loading is not an excuse to eat all your favorite comfort foods in one day. It’s a nutritional strategy, which means you’ll need to approach it in a very calculated manner, without under-eating or overconsuming carbohydrates.

As mentioned earlier, a good rule of thumb to follow is 4.5 grams of carbs per pound of body weight  (10 grams per kilogram). Some people might need more or less than that, but while you’re still figuring that out, 4.5 grams is a safe bet.

Experiment Early in Your Training Cycle

When carb-loading, it’s essential to stick to foods that you know (and that your stomach is familiar with!). This is not the time to experiment with new foods or take recommendations from other runners, because you might end up with an upset stomach. The worst thing you can do when it comes to carb-loading is to wait until race week to try out your carb-load. If your stomach doesn’t agree with your choice of carbohydrates, your race could go from great to not so good.

Your body might be in for a small shock when you suddenly consume more carbs than usual, so be kind to it by choosing carbs that it’s already familiar with.

What Foods Are Good For Carb-Loading?

When you’re carb-loading, you must remember that not all carbs are right for you. The best thing you can do is aim for high-carb foods that are also low in fat and fiber. Good examples of this include rice, pasta, cereals, and even bread.

These days, there are plenty of carb-loading supplements and pre-made food items like nut bars, powders, and running gels. These products are great, but you should remember that they’re not a necessity and that you can carb-load without spending too much money.

If you think about it, you probably already have everything you need to carb-load sitting in your fridge or pantry right now.

How Much Should You Eat?

There is no one-size-fits-all solution when it comes to carbohydrate-loading. Our bodies are different, so we must use trial and error to determine how much we should eat for a carb-load.

As a rule of thumb, 4.5 grams of carbs per pound of bodyweight every 24 hours is an average amount you should consume throughout your carb-load.

If you find that fatigue sets in sooner than it should, you could always try increasing your carb intake the next time around. Or, if you feel like 4.5 grams is too much, you could always lower the amount to whatever feels right in your body.

Experimenting with carb intake will require time and effort on your part. But once you’ve identified the sweet spot, the ideal amount of carbs, then you’ll be able to maximize your performance during a marathon or long-distance run.

How To Time Your Carbs

As a nutritional strategy, carb-loading is more than just about how many carbs you eat or from what sources. It’s also a matter of timing. Typically, that timing will depend on the carb-loading regimen that you’ve chosen for yourself.

So, if you’ve decided to try out a one-day carb-load, you’ll be eating your carbs the day before. Some running events even offer high-carb meals to runners the night before the race, knowing that most of them will be carb-loading.

Plus, one meal is not enough to completely replenish your glycogen stores. So, you’ll need to consume multiple high-carb meals to get the effects that you want.

Whatever it is, you shouldn’t eat too heavily in the moments right before your run. Eating a heavy meal before any intense physical activity is bad news, and could leave you cramping up quickly.

Suppose you want to consume carbohydrates right before the race begins. In that case, it’s best to consume it in a more straightforward form like liquids or the running gels mentioned earlier.

After The Run

People often forget that carb-loading also needs to happen after the run is over. Think about it: after you’ve been running for hours, your glycogen stores will be at their lowest yet again. So, you’ll need to eat a full meal to replenish all your stores.

This after-race meal shouldn’t be pure carbs, though. A healthy 3:1 ratio of carbs to protein is essential to help you replenish your glycogen while also helping to repair your aching muscles.

Does Carb-loading For A Marathon Really Work?

Carb-loading is a widespread practice among marathon runners and other endurance athletes. It’s not just a fad that people have passed around like an urban legend over the years. In truth, it’s a well-researched and thoroughly tried and tested nutritional strategy for anyone wanting better performance on their run.

Still, as mentioned before, people must understand that carb-loading is only necessary for sports that last longer than 90 minutes. Why 90 minutes? Because that’s the average amount of time for muscle and liver glycogen to deplete for most people.

Considering how the average runner takes 4-5 hours to complete a full marathon, carb-loading is indeed a useful nutritional strategy.

If you need additional proof to convince yourself that carb-loading is effective, speak to other runners who have more experience than you. Learning about carb-loading from them will increase your confidence in deciding whether or not you should try it out yourself.

Final Thoughts

If you’d like to include carb-loading as part of your training regimen, be sure to consult a doctor first. That way, you can be sure that there aren’t any issues with you adopting this eating strategy ahead of your next long-distance run.

To avoid or minimize rookie mistakes on your part, you could also speak to whoever you train with. The odds are that they’re more experienced than you when it comes to carb-loading. You can benefit from that as they advise and motivate you through your carb-loading process.

Lastly, remember that carb-loading isn’t a replacement for intense training and physical conditioning. While eating additional carbs will help you fight fatigue for much longer, it’s really your mind and your body that’ll get you through the finish line.



Coach Scott is a published author and RRCA certified running coach (Level 2). He has published over 20 books including, Beginner's Guide to Half Marathons: A Simple Step-By-Step Solution to Get You to the Finish Line in 12 Weeks! (Beginner To Finisher Book 3), which has become an Amazon International #1 bestseller. Scott specializes in helping new runners become injury-free race finishers. He recently completed his 14th half marathon race. 

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What is Carb Loading? Why Do Long Distance Runners do this?
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