Carbohydrate Loading 101
Carbohydrate Storage: Glycogen
It’s well recognized in the sports nutrition field that carbohydrates are a key macronutrient for optimal performance, especially in endurance sports. Carbohydrates provide a readily available fuel source during physical activity, particularly as exercise intensity increases. Carbohydrates are digested and broken down into simple sugars, like glucose, which are then transported into the bloodstream for energy. Glucose can be linked back together to form tight, branched chains of glycogen molecules, which provide essential fuel stores during prolonged exercise.
Glycogen is the “storage form” of carbohydrates in the body. We have glycogen stores in our liver and our skeletal muscle. Glycogen stores in the liver are relatively modest, approximately 80-100 grams, and are typically used to release sugar back into the blood to maintain blood glucose levels between meals and overnight. Glycogen stores in the skeletal muscle are larger, typically several hundred grams, and provide a readily available local fuel source for working muscles during physical activity (1). Inadequate glycogen stores and/or inadequate carbohydrate supplementation during exercise can hinder our ability to meet our energy demands and compromise performance (1). With that in mind, we want to have fully stocked glycogen stores. This requires both a commitment to eating adequate carbohydrates daily and a commitment to a proper carbohydrate loading strategy prior to certain events, races, and competitions.
Daily Carbohydrate Needs
In order to achieve adequate glycogen storage, we need to first eat a daily diet with adequate carbohydrates to support our activity level. In general, higher volumes of training require more total calories and more carbohydrates.
Below is a summary of guidelines for carbohydrate intake based on training, which can be used as a starting point for estimating your daily carbohydrate needs (2).
Light activity, low intensity, skill-based activity = 3-5 grams (g) of carbohydrate/kilogram (kg) of body weight
Moderate activity for ~1 hour per day = 5-7 g carbohydrate/kg bodyweight
Moderate to high intensity activity for ~1-3 hours per day = 6-10 g carbohydrate/kg bodyweight
Moderate to high intensity exercise for ~4-5+ hours per day = 8-12 g carbohydrate/kg bodyweight
Carbohydrate Loading Guidelines
On top of adequate daily carbohydrate intake, we can use a highly effective sports nutrition strategy called “carbohydrate loading” (often shortened to “carb loading”) to maximize glycogen stores prior to an event. Carbohydrate loading is particularly important for longer duration events.
For events under 90 minutes, a formal carbohydrate loading protocol is generally not necessary. Instead, athletes should focus on maintaining adequate daily carbohydrate intake and consuming a carbohydrate-rich meal and/or snack in the hours leading up to the event.
For events longer than 90 minutes, a formal carbohydrate loading protocol can be implemented to optimize performance. Carb loading involves consuming 10-12 grams of carbohydrate per kilogram of body weight for the ~36-48 hours leading up to competition (1,3). For the 150 pound (lb) (~68.2 kilogram) runner, this means eating about 681-818 grams of carbohydrates per day for the ~1-2 days leading up to an event. If consuming 10-12 g carb/kg over 36-48 hours feels overwhelming, starting your carbohydrate increase earlier and spreading it over several days may be a more manageable strategy. For example, some athletes may choose to aim for ~8 g carbohydrate/kg spread over ~3-4 days prior to the event to make it more manageable (note that this is a practical strategy to consider experimenting with, not a research-backed protocol).
Carbohydrate Loading Implementation
Determine Your Carb Loading Intake Goal
The goal of carbohydrate loading is to increase the proportion of intake that comes from carbohydrate sources. While carbohydrates might constitute anywhere from 45-65% of your regular daily intake, carbohydrates will make up a much larger proportion of your intake on carbohydrate loading days. A proper carbohydrate load requires you to shift your macronutrient distribution so that you are prioritizing carbohydrates at the expense of protein and fat.
One straightforward approach to planning and implementing a carbohydrate load is to calculate your daily carbohydrate intake goals based on the guidance above (10-12 g carbohydrate/kg), then review the nutrition facts labels on the foods that you consume (or plan to consume) to make sure that you are meeting your numeric goal, or at least getting close to it. It might be helpful to use a food tracking platform (e.g. Cronometer, MyFitnessPal) to help you with the math, or you could simply tally up the grams of carbohydrate planned/consumed using pen and paper.
If you’re new to carbohydrate loading or you don’t feel comfortable working with numbers and tracking your intake, you can take a simpler approach using the following steps:
Add an extra portion of carbohydrate to each of your meals at the expense of other foods.
Incorporate carbohydrates into all of the snacks that you consume throughout the day.
Add a carbohydrate-rich evening snack or dessert, like dates, fruit sorbet, or a large bowl of cereal with a banana.
Sip on carbohydrate-containing beverages (sports drinks, juices, soda, etc.) throughout the day.
Select Carbohydrate-Rich Foods
When it comes to carbohydrate loading, the type of carbohydrate matters. In normal daily life outside of performance nutrition, we typically want to prioritize high fiber, complex carbohydrates, such as beans, whole grains, and fibrous fruits/vegetables to support our health. During a carbohydrate load, you’ll want to emphasize lower fiber foods so that you’re able to tolerate the high volume of carbohydrates without causing gastrointestinal distress or other types of discomfort. Items like sports drinks, fruit juices, applesauce, bagels/rolls, white bread, pancakes/waffles, low fiber cereal, pretzels, fig bars, honey, jam, graham crackers, and animal crackers are all good examples of low fiber, high carbohydrate foods to consider incorporating during a carbohydrate load.
Liquid calories like sugar-sweetened beverages (e.g. sports drinks, soda, juices, smoothies) are great options to augment carbohydrate intake from meals and snacks as they are typically convenient, easy to get down, and may be less likely to cause feelings of over fullness. You could even sprinkle in some sports nutrition gels, chews, or candy across the day to give you a boost toward your intake goal.
In order to avoid excessive fullness, be mindful of high fat and high protein foods in addition to high fiber foods, all of which can contribute to greater satiety and fullness. Again, these foods are not bad, but they generally increase fullness and will generally make it harder to consume enough carbohydrates to meet your carb loading goal. Additionally, you should plan to spread your carbohydrate intake across the day to maximize your chance of meeting your intake goal. Simply adding an extra serving of pasta to your dinner will not cut it.
Practice Meeting Your Carb Goal
Try to practice your carbohydrate load at least once before your event. Pick a long run, ride, or session that will last longer than 90 minutes and test out different combinations of carbohydrate-rich meals and snacks to start familiarizing yourself with the logistics of a carbohydrate load.
Weight Changes
Your body usually stores at least 3 grams of water per every 1 gram of glycogen, which means that you may feel “puffy” or experience temporary weight gain during a carbohydrate load due to fluid retention. This is normal and physiologically appropriate. The extra water stored alongside glycogen contributes to your overall body’s water stores (4).
If you’re in the habit of weighing yourself regularly and you think it might feel distressing to see your weight increase by a few pounds due to the carbohydrate load, consider taking a break from the scale in the days leading up to the race. If a carbohydrate load feels uncomfortable because you’re navigating a tricky relationship with food and your body, try to zoom out and remind yourself that a carbohydrate load only lasts for a couple of days and you’re using it to improve your performance. Food is what fuels you and you need to eat enough to be able to do the activities that you love and perform your best.
Sample Carbohydrate Loading Day
While you may think that you eat a lot of carbohydrates in your daily diet, you’d be surprised at how much effort (and food!) can be required to meet such high numeric goals during your carbohydrate load.
Let’s revisit the 150-lb (~68.2 kg) athlete who has a daily carbohydrate intake goal of about 681-818 grams. Here’s what a day of eating might look like during their carbohydrate load:
Breakfast =1 plain bagel with 3 tablespoons strawberry jam + 1 large banana + 12 ounce glass orange juice (= ~145 g carbs)
Snack = 2 cups honey nut cheerios + 1 cup 1% milk + 3 Medjool dates (= ~120 g carbs)
Lunch = 2 cups cooked white rice + 3 ounces cooked chicken breast + ½ cup teriyaki sauce + 2 pouches Welch’s fruit snacks (= ~160 g carbs)
Snack = 2 ounces mini pretzels (about ~40 mini pretzels) + 24 ounces Gatorade sipped during lunch and remainder of afternoon (= ~88 g carbs)
Dinner = 2 cups cooked spaghetti + ¾ cup marinara sauce + 3 ounces cooked turkey meatballs (= ~110 g carbs)
Dessert = 1 cup fruit sorbet (= ~65 g carbs)
Daily total = ~ 690 g+ carbs (= ~10 g carbs/kg body weight)
* This example demonstrates how to reach the lower end of a carbohydrate loading target. Athletes aiming for 12 g carb/kg will need additional carbohydrates. This is one example of how an athlete might reach their target with a sample day of eating; individual needs and food choices will vary. Estimates/numbers may also vary depending on brand and exact food item consumed.
Executing a proper carbohydrate load requires advanced planning, preparation, and practice, and I’m here to help! We can build a customized carbohydrate loading and race-day nutrition plan tailored specifically to your body, dietary preferences, and performance goals. Reach out to me with questions or book an appointment to work together 1:1 if you’re looking for additional support.
References
Cao W, He Y, Fu R, Chen Y, Yu J, He Z. A Review of Carbohydrate Supplementation Approaches and Strategies for Optimizing Performance in Elite Long-Distance Endurance. Nutrients. 2025;17(5):918. Published 2025 Mar 6. doi:10.3390/nu17050918
Burke LM, Hawley JA, Wong SH, Jeukendrup AE. Carbohydrates for training and competition. J Sports Sci. 2011;29 Suppl 1:S17-S27. doi:10.1080/02640414.2011.585473
Burke LM, Castell LM, Casa DJ, et al. International Association of Athletics Federations Consensus Statement 2019: Nutrition for Athletics. Int J Sport Nutr Exerc Metab. 2019;29(2):73-84. doi:10.1123/ijsnem.2019-0065
Fernández-Elías, V.E., Ortega, J.F., Nelson, R.K. et al. Relationship between muscle water and glycogen recovery after prolonged exercise in the heat in humans. Eur J Appl Physiol 115, 1919–1926 (2015). https://doi.org/10.1007/s00421-015-3175-z