What is Carb Loading and How Do You Carbo Load?

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You may have heard of carb loading as a strategy to boost physical performance during endurance exercise and competition. The strategy has substantial scientific backing and is relatively easy to follow once you choose a specific method. Learn about carb loading and how to do it below.

Carb Loading

Carb loading is a nutritional strategy most often used by endurance athletes to increase stored energy in the form of glycogen for better performance. Carbohydrates, which provide the glycogen, are consumed in high amounts a few days or directly ahead of a competition or training session. Usually, this practice is combined with reduced activity to better preserve the glycogen stores being created.

While your body needs proteins and fats as well as carbohydrates, carbs are the macronutrient most efficiently metabolized for energy. When more carbohydrates are consumed than the body can use right away, the excess glycogen is stored in the liver and muscles for later use.

Glycogen is the stored form of carbohydrates. Excess glycogen is stored 80% in the muscles and 20% in the liver.

How is Carb Loading Beneficial?

Glycogen is the body’s preferred and most accessible energy source. Glycogen is stored in your muscles and liver, and when you perform any activity, the body draws on the stores you have available. Your stored glycogen is then sent to your muscles during intense exercise.

For regular activity or shorter workouts, the amount of glycogen you have is often enough. But extra glycogen, along with carbohydrate consumption during exercise, may be necessary for those pursuing activities for a long duration or for activities that are more intense. Typically refueling during exercise is needed beyond 60 minutes of exercise when the workout intensity is high.

To provide that extra energy and prevent fatigue, consuming a large number of carbohydrates can be beneficial. Available glycogen stores and their depletion are considered a limiting performance factor, meaning that running out of this fuel source can prevent you from doing your best.

Who Should Try Carb Loading

If you are going to be exercising for more than 90 minutes, carb-loading could be worth trying. But, for recreational or personal training sessions, carb-loading may not be necessary.

Still, if you are hoping to beat a personal best or competing in an event, this nutritional strategy could give you the boost you need to succeed. Carb loading is most often used by endurance athletes or for prolonged sports with intense bursts such as:

The basic recommendation is that any activity that relies on the aerobic system more than 25% benefits from carbohydrate loading.

When to Try Carb Loading

If you are attempting carb-loading for the first time, you may wish to give it a trial run before an important competition to see how your body responds. Some people may find that overconsuming carbs makes them feel heavy or sluggish. Or, they may need to monitor the timing and type of carbs they eat closely.

After a trial run with carb-loading, you may decide you like how it impacted you. In this case, use this technique before a competition as a strategy to boost performance. 

How to Carb Load

Most people can store about 1,800 to 2,000 calories in their liver and muscles as glycogen fuel. These stores will provide energy for 60 to 90 of vigorous activity.

Research suggests a high carbohydrate intake of 10 grams per kilogram (4.5 grams per pound) of body weight the day before a competition and approximately 24–36 hours from the last training session is ideal if you want to carb load.

The number of carbohydrates you will need can vary, with studies suggesting 8 grams and up to 12 grams per kilogram (3.6 to 5.5 grams per pound) of bodyweight being optimal. The table below indicates what that would look like for some specific body weights.

 Bodyweight (lb)  Carbs (g)  Total Calories from Carbs
 130lb  468-715  1,196-2,860
 150lb  540-825  1,380-3,300
 200lb  720-1100  1,840-4,400

Three-Day Carb Loading Strategy

A 3-day carb-loading strategy is most common and likely the most effective. Begin 72 to 96 hours before your event. Here's how to implement this strategy.

  • Adjust total carbs: Athletes should ingest about 8-10 grams of carbohydrates per kilogram of weight per day with low volume of exercise to maximize glycogen stores.
  • Taper your training: Decrease the duration and intensity of training during this time to preserve the glycogen stores that you are creating. Reduce duration and intensity by 50%.
  • Maintain hydration: Fluid intake should be at least 1ml of fluids or water per calorie intake, so if you're eating 3,000 calorie in a day, you should be drinking 3 liters of water. Or you may also do the urine test, making sure your urine is tinted yellow.
  • Choose familiar foods: On the day of the event, choose foods that you ate during training and avoid introducing new foods in case of an adverse reaction. 
  • Consume complex carbs: Getting enough fiber by choosing complex carbohydrates is likely ideal because low fiber carbs can increase the likelihood of gastrointestinal distress or diarrhea. Choose foods that are below 55 on the glycemic index. And avoid meals that are too heavy or fat-rich.

What Are Carbs?

Carbohydrates are either simple or complex. Simple carbohydrates digest quickly and convert readily into glucose. These are foods such as juices, sugar-sweetened beverages, candy, white sugar, and honey.

Complex carbohydrates digest slower, providing a more sustained release of glucose and contain more fiber and nutrients. These are foods such as brown rice, whole-grain bread, whole fruits, vegetables, beans, and legumes.

Event Day Strategy

Four hours before your event begins, consume 1-4 grams of carbohydrates per kilogram of body weight, especially if the high-intensity exercise will be greater than 90 minutes.

Then consume closer to 0.8 grams per kilogram of body weight of carbohydrates at least 60 minutes before performance. Some people may be able to tolerate intake at 30 minutes before performance without having a "hypoglycemic rebound" if they stretch beforehand or train with this eating pattern. If you cannot tolerate food, you may consider drinking a 6.4% carbohydrate drink.

Importance of Carbohydrate Types

Some studies have suggested that choosing carbohydrates low on the glycemic index—meaning those that release into the bloodstream at a slower rate—are best for carb loading because they provide a steadier stream of energy. However, this concept has been debated.

Most research confirms that the choice of carbohydrates—whether high or low on the Glycemic Index—is not important or is more dependant on the individual’s sensitivity to glycogen. Furthermore, the type of carbohydrate, timing, and the amount that each athlete requires for optimal performance is unique to them.

If you choose to carb load before an event, you will still likely need to supplement more carbohydrates during the activity. During exercise, consume 30 to 60 grams of carbohydrates every hour in a 6%-8% carbohydrate-electrolyte solution (6-12 fluid ounces) every 10 to 15 minutes.

Food for Carb Loading

  • Apple 
  • Bagel 
  • Banana 
  • Beans
  • Corn
  • Cup of oatmeal 
  • English muffin
  • Juice
  • Milk
  • Peas
  • Potatoes
  • Quinoa
  • Slice of bread
  • Sweet potatoes

A Word From Verywell

Carb loading might be an effective strategy for those looking to boost performance during prolonged, intense activity. Consuming more carbohydrates along with reduced activity for a few days before an event might preserve and load the body with energy stores in the form of glycogen.

However, this strategy is not necessarily going to work for everyone, and the type, timing, and amount of carbs required will be unique for each person. Other factors such as recovery, fitness level, and hydration can also affect performance. Experiment with carb loading before a big competition to determine how your body responds.

5 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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  2. Kanter M. High-quality carbohydrates and physical performance: Expert panel report. Nutr Today. 2018;53(1):35-39. doi:10.1097/NT.0000000000000238

  3. Kerksick, C.M., Arent, S., Schoenfeld, B.J. et al. International society of sports nutrition position stand: nutrient timing. J Int Soc Sports Nutr 14, 33 (2017). doi:10.1186/s12970-017-0189-4

  4. Mata F, Valenzuela PL, Gimenez J, et al. Carbohydrate availability and physical performance: Physiological overview and practical recommendations. Nutrients. 2019;11(5):1084. doi:10.3390/nu11051084

  5. Burke LM, Hawley JA, Wong SH, Jeukendrup AE. Carbohydrates for training and competition. Journal of Sports Sciences. 2011;29(sup1). doi:10.1080/02640414.2011.585473

By Rachel MacPherson, BA, CPT
Rachel MacPherson is a health writer, certified personal trainer, and exercise nutrition coach based in Montreal.