Carb Loading

What’s Included?

  • What is carb loading
  • When to carb load
  • How to carb load
  • Best sources of Carbohydrates

As runners and endurance athletes, carbohydrates are our best friend. Carbohydrates are our bodies preferred fuel source and are easy to use. This article will explain what carbohydrate (carb) loading is, when to carb load, and how to properly carb load.

What is Carb Loading?

When we eat carbohydrates, what we don’t use right away then gets stored in our muscles and in our liver in the form of glycogen. When our body doesn’t have enough carbohydrate coming in, it can begin to break down and use glycogen as a source of glucose and energy. Carb loading is a way to maximize glycogen stores prior to exercise for optimal energy availability. Also, it’s important to note that for every 1 gram of carbohydrate your body stores as glycogen, it also stores 3 grams of water. Carb loading may contribute to short term weight fluctuations and feelings of bloating.

How do you Carb Load?

There are multiple strategies for carb loading:

1.) 3 days of hard training on a low carbohydrate diet (<5 g/kg carb intake), followed by 3 days of tapered training with a high carb diet (8-10 g/kg carb intake)

2.) 3 day exercise taper with a high carbohydrate diet (8-10 g/kg carb intake) with 24 hours of full rest prior to race

3.) 6 days out moderate depletion, complete long run without additional fuel during (only water), followed by moderate/normal carb intake for 3 days and lower intensity runs, and 3 days of high carbohydrate with low intensity workouts or rest

4.) 1 day of hard training to fully deplete glycogen stores, followed by 24 hours of high carbohydrate intake (8-10g/kg) and full rest


To find your weight in kilograms (kg) divide your weight in pounds (lbs) by 2.2 to get kilograms. For example: a 150 lb. runner would be 68.1 kg. Multiply this by 8-10 to get grams of carbohydrates needed to carb load. This person would need approximately 544 grams of carbohydrate to fully carb load.

What are the Best Sources of Carbs?

You’ll want to decrease fiber and the amount of fat you consume as you get closer to race day in order to avoid potential stomach issues. With that in mind, here are some good sources of carbohydrates:

  • Low fiber grains (breads, pastas, cereals, rice, oats, etc)
  • Fruit
  • Starchy vegetables (Potatoes, peas, corn, squash, beets, etc)
  • Fruit juices or other carbohydrate-containing beverages & liquid calories

It’s good to practice your race day and race week fueling plan at least once during a training cycle to make sure what you’re doing works for you. Remember that carb loading is most beneficial for exercise that lasts greater than 90 minutes. Carb loading is not significantly more effective for 5-10k distances and events less than 90 minutes. You can also check out Team USA’s “Athlete Plates” for visuals on how to build your plate depending on your training intensity.

Amy Haas
Run with Aim, LLC
UESCA Certified Running Coach
NASM Certified Personal Trainer
NASM Certified Nutrition Coach

Information provided & verified by:
Katelyn Biros, RD
Registered Dietitian

PMID: 29444266
PMID: 12048325
PMID: 28919842