Emily Brown

Written by Emily Brown


3 Ways to Effectively Carb Loading Before a Race

Carbohydrate loading, also referred to as carb loading, is a familiar term among athletes of all sports, but especially in the world of running.

Carb loading before marathon events can help prepare us for success on race day, but it is not just for marathon runners, but all endurance events.

To most of us, it is often used to describe a large pasta dinner the night before a race or the consumption of massive amounts of carbohydrate justified by statements such as “I run a lot, so I can eat this.”


Us too!

It is true that carbohydrate is the body’s major fuel source and is a crucial component of the distance runner’s diet.

However, true carbohydrate loading is a systematic and scientific practice that takes course over the weeks and days leading up to competition, usually a marathon or ultra marathon with the purpose of maximizing the storage of glycogen in muscles.


If you are thinking of taking your race week eating to the next level, you could consider carb back loading, but we found carb back loading results were not as impressive as once thought.

If you are looking for the best food for carb loading, we have a carb loading diet for you to follow, but today, we are going to explain the who, what, when, why and how of carb loading and tips for how you can us it to race as fast as you can.


We explain the who, what, when, why and how of carbo loading and give you tips based on your training circumstances to run your fastest marathon or ultra.

Carb Loading for Runners and Endurance Sports

Carbohydrate loading is only effective for endurance events lasting longer than 90 minutes, such as marathons, ultra marathons, and triathlons.

During intense, continuous endurance exercise, your muscles will become depleted of glycogen after about 90 minutes.

Carb loading is meant to store extra glycogen that your muscles can tap into once the normal stores are used up.

Carbohydrate loading is not useful for events like a 5k or 10k since the running effort will not be long enough to completely deplete muscle glycogen stores.

Any extra glycogen in the muscles during those events may actually be detrimental to performance due to the potential of muscle stiffness and heaviness that can be associated with carbohydrate loading.

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Why Does Carb Loading Before a Race Work?

Muscle glycogen is the main source of energy in intense endurance events.

As that glycogen is used up, athletic performance is jeopardized.

However, the greater the amount of stored muscle glycogen, the greater the endurance potential of the body.

How to carb load before a marathon (or endurance event)

As carbohydrate loading received more attention for its ability to improve athletic performance in endurance events, more research has focused on effective methods.

The traditional method consisted of tapered training accompanied by increased carbohydrate consumption in the weeks leading up to competition.

A similar method followed this same model but in a shorter duration of time (6 days).

There are also more rapid methods of carbohydrate loading that seek to maximize glycogen stores in the final 24 hours before competition.

Here’s the deal:

The appropriate method for you depends on the event you are doing, your training leading up to the event, and the number of events you plan on doing throughout the year.

While some athletes may practice a long taper leading up to a major competition, others prefer to keep a high level of training all the way up to the day of the event.

Below are some examples of carbohydrate guidelines according to which method you may choose.

Carb Loading Method 1: Long Taper

Using the long taper method, you should have your final hard training session 3 weeks before competition day.

By 2 weeks out, you should really start tapering your training. Just make sure you do not make the 3 most common tapering mistakes!


During this taper time you do not need to eat extra calories since your body will not be using as many as it needed during training. Instead, you should continue to eat 3-5 grams of carbohydrate per pound of body weight and reduce your fat intake to make up for your body’s reduced demand for energy.

Your muscles will use these extra carbohydrate calories to build up a glycogen store that will remain, since you won’t be using it for training any longer. Normally your body can store glycogen at the capacity of 80-120 mmol/kg.

When practiced perfectly, this method of carbohydrate loading should allow you to almost double that storage capacity to approximately 200 mmol/kg.

[bctt tweet=”Helpful post from @Runners_Connect will help you determine your carbo-loading needs.” via=”no”]

Carb Loading Method 2: 6-day Protocol

In this method, a glycogen-depleting exercise is performed 6 days prior to the event.

This exercise should utilize the same muscle groups that will be used in competition, so if you are planning on following a marathon training schedule, you would want to add in a few minutes of very intense sprinting to deplete your muscle glycogen stores.

The next 3 days would consist of a normal mixed diet (~2-3 grams of carbohydrate per pound), and tapered training.

Then 3 days before competition you would further reduce training or rest completely and consume a high-carbohydrate (~4.5 grams per pound), low-fat diet.

Carb Loading Method 3: Rapid Loading

This method doesn’t require the athlete to taper in the weeks leading up to competition.

Perhaps this athlete has more competitions to be prepared for soon after, hasn’t done enough training leading into competition and needs those last few weeks, or simply performs better physically and/or mentally without a taper.

You might be wondering what to do in this situation:

Whatever the reason, it is possible to achieve comparable glycogen storage results using a 24-hour carbohydrate loading method.

To do this, the athlete will perform an intense glycogen-depleting exercise 24 hours prior to competition.

Immediately following this workout the athlete will start to consume a high-carbohydrate diet consisting of 5-6 grams of carbohydrate per pound and continue this throughout the day.

As an example, an athlete weighing 150 pounds would need to eat about 750 grams (or 3000 calories worth) of carbohydrate. To make room for all of these carbs you would need to greatly reduce your intake of fat and protein for that day.

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The guide contains a plan of exactly what you should be eating in the 5 days to 3 hours before your race. We give specific food recommendations to make sure you are ready on race day.

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How to Carb Load for a Race

Whatever method you choose, there are some things to keep in mind.

First, as always with any dietary changes, try out carbohydrate loading methods BEFORE you use them in competition.


Especially with the rapid loading method, intestinal problems may occur and you do not want to have to deal with these on race day.

In the weeks and days leading up to competition, continue to eat an adequate amount of protein (0.6-0.7 grams per pound). Protein may be helpful in assisting glycogen synthesis and can also be used as a secondary fuel source in endurance exercise.

Add some fiber-rich foods to promote regular bowel movements but don’t go overboard.

Too many refined carbohydrates can result in constipation but too much fiber could cause diarrhea and intestinal distress on race day.


You need to expect some weight gain (~2-4 pounds), and not panic about it.

Here’s why:

For every ounce of glycogen the body also stores 3 ounces of water.

Although your muscles may feel a little heavier at the beginning of the race these feelings will subside as the body uses up the glycogen and water throughout the race.

Use various forms of carbohydrate-dense foods and drinks to meet your needs such as juices, gels, and sports drinks. Be sure to consume whole-grain sources as well to balance out all that sugar.

Here are some of the best carbohydrates for runners.

But wait:

Do not wait until your last meal to load up on the carbohydrates.

You want to give your body time to digest and a big meal at night may leave you feeling full and uncomfortable in the morning.

Instead trying eating your largest meal early in the day prior to competition. Here are 6 other important nutrition tips for the marathon taper.

Finally, be sure to still consume some energy sources and fluids during your event.

What you have stored up will help you go longer, but it still may not be enough to get you through the entire race without an additional fueling plan.

[bctt tweet=”What a great post from @Runners_Connect with 3 Methods to Carbo-load depending on your training background!” via=”no”]

Free Marathon Nutrition Course

The Simple 3 Step Calculation To Vanquish The Marathon Bonk

Here’s what we’ve got for you

How to calculate your exact glycogen storage and carbohydrate use so you know exactly how much you have to refuel

How to calculate your sweat loss and re-hydration rate to maintain optimal performance.

How to develop your individualized fueling plan using you sweat rate and glycogen usage.


Houmard JA, Costill DL, Mitchell SH, Park RC, Hickner, Roemmich JN. Reduced training maintains performance in distance runners. Intl J Sports Med. 1990;11(1):46-52.
Sherman WM, Costill DL, Fink WJ, Miller JM. The effect of exercise and diet manipulation on muscle glycogen and its subsequent use during performance. Int J Sport Med. 1981;2:114-118.
Fairchild TJ, Fletcher S, Steele P, Goodman C, Dawson B, Fournier PA. Rapid carbohydrate loading after a short bout of near maximal-intensity exercise. Med Sci Sport Exerc. 2002;34:980-986.

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4 Responses on “3 Ways to Effectively Carb Loading Before a Race

  1. Big fan of method three, which I think is often referred to as the Western Australian CHO Loading protocol.

    As long as you’re comfortable with doing such an effort the day before a marathon, that would be my preferred option.

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