The Aid Station: Carboloading

June 27, 2022

The long-standing joke for half marathoners and full marathoners is to carb-load the night before with a big plate of pasta.

The truth is, much more planning goes into proper pre-race nutrition than just simply overloading the night before. More importantly, if you planned on doing it all in one meal, you may end up hindering your performance with fatigue, gut issues, and inflammation.

For those of you who are just starting your running journey you may be wondering, what is carb-loading? Carbohydrates in the form of glycogen are your body’s preferred fuel and for races lasting longer than 1.5-2 hours, filling up these fuel stores are key to helping you go the distance.

Athletes need carbs to maximize the stores of glycogen in their muscles and liver. Your body only has so much room for this fuel source, so carb stores are needed to help you maintain your energy. Ever hear someone say they, “hit the wall” or “bonked”? These terms are other favorites and refer to your body running out of fuel. When you run out of your energy source your pace may start to slow, your muscle will cramp, and fatigue will set in. Through carb-loading, athletes have excess carbs stored in the liver making it easier for their bodies to release during races and long runs. Carbs also help with hydration. For every gram of stored glycogen there are four grams of water stored along with it. Hydration is extremely important factor when racing.

What does carbo loading look like?

It is always a good idea to gradually introduce any new stimulus into a training or nutrition plan. Carb-loading should be no different. Runners should prepare to increase their carb intake little by little prior to their event. This will ensure you have excess glycogen in your liver for your muscles to feed from during endurance exercises.

What are some best practices for carb loading?

Typically, you should start carb-loading three to four days out from a race. In general, you will need to slowly add more of a mixture of carbohydrates such as rice, legumes, potatoes into your meals. As you gradually increase your intake of carbs per meal, you will want to eat less fat and fiber.

Carb heavy meals, without practice and nutrition training on the gut, can cause extreme stomach upset. Be sure not to go overboard on the carbs.

The day before the race, stick to only simple carbs that are easily digestible.

Common Mistakes When Carb Loading

Consuming all the carbs in one sitting

Doing this does not give your body enough time to fill its stores properly. It can leave you lethargic for the rest of the day and the following morning!

Eating more than you usually do

You’ve worked so hard in your training, do not deviate too much from what you have done in your build up. Yes, it is important to top off your glycogen stores, but it does not mean “stuff yourself” to get fuller glycogen stores. You are simply adjusting each meal to have a larger carbohydrate component.

Don’t look at the scale

Gaining weight while carb-loading is natural. That’s because carbs help you retain water. Remember that for every gram of stored glycogen, you’re storing 4 grams of water. If you gain some weight, that’s a good thing. It means your body has the fuel and hydration ready to race.

Eating too much fiber

As you increase your carbs, runners should reduce their fiber intake in the last three days prior to a race. This is because fiber can be taxing on the GI system.

Experimenting with carb loading for the first time

You never want to “try” something new on race day. It is best to always plan ahead of a couple of long runs in your build up with some carb loading meals so that you know what to expect and how your body will respond.

Practicing will help you dial in your carb-loading plan just like you dial in your race nutrition plan. Then, once you know what works best for you, pre-plan your meals the last three days so you cannot stress about what to eat.

Not eating enough carbs

Runners typically eat healthy and know how to fuel themselves during their training. Race week can be a slight exception for those following low carb eating habits.

Not drinking enough when carb loading

Not all carbs are created equal.

There are different types of sugars: fructose, sucrose, glucose. Different carbohydrates have different ways to reach the bloodstream. Therefore, runners need to consider of what they’re drinking with what carbs they’re eating.

“Sports drinks contains fructose, glucose, and sucrose which are different sources of carbohydrates. They contain some sodium which helps with the transportation of glucose, meaning sodium is an important part of carbohydrate utilization.” Running, and more specifically faster or higher intensity aerobic running, predominantly uses glycogen which is the body’s stored carbohydrate source. Eating a high proportion of carbs in the days leading up to an important race can ensure that glycogen stores are topped up, thus providing a runner with the maximum available fuel for the upcoming hard effort.

Do all races require carbo loading? No.

The body has enough glycogen stored to last for about 75-90 minutes. For most runners, this equates to doing a 5K, 10K, 15k, and maybe a half marathon without having drained glycogen stores. If this is the case, and assuming you already eat carbs as part of a healthy diet, you shouldn’t worry about carbo-loading before the race. As it was mentioned earlier, eating too many carbs may hinder your performance as you may feel bloated or lethargic the next day due to the additional water retained as part of the glycogen building process and ingesting too many carbs.

Those who are running 75 minutes or more however—running a half-marathon, marathon, and ultra-marathon it would be well advised to consider adding extra carbs to their pre-race diet. Again, it is recommended to do this in the two-to-three days prior to the race given that you have already practiced this method in a couple long runs.

A good guideline is to aim for seven to eight grams of carbs per kilogram body weight three days before the race; eight to 10 grams per kilogram two days before and 10 to 12 the day before. This will ensure that your glycogen stores are topped up and provide you with the most available stored fuel for the race.

If you find yourself in a situation where you have not practiced carb-loading, do not worry! This will not make or break your race. It won’t undo any of the training you’ve put in. Your race day nutrition can will play a huge role in managing your energy stores during the race.