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Carbohydrate Needs for Runners

by: Brian Cook, Ph.D


Some of my favorite memories of running cross country and track in high school and college were the pasta dinners before big races. These gatherings provided a great opportunity to relax, socialize, and, most importantly, load up on much needed carbohydrates to fuel our race day performance. My teammates and I never questioned whether this pre-race day ritual actually lowered our times; but should we have? Was our pasta binge actually helping us attain peak performance or was the socializing and relaxation helping to lower our times more than the carbohydrate-packed dinner?

Runners are often taught that loading up on carbohydrates before a race will facilitate a run at their peak ability. Superficially, this recommendation makes sense because carbohydrates are the primary energy source for moderate to intense level exercise. General recommendations for a healthy diet are to get between 45 -65% of your daily calories from carbohydrates. Thus, for a typical 2000 calorie per day diet, one would need approximately 300 grams of carbohydrates (approximately 60% of daily calories or 1200 calories, coming from carbohydrates). This amount will provide instant energy by quickly converting simple carbohydrates into blood glucose (energy that is immediately available to fuel exercise) and storing the remaining carbohydrates as glycogen (energy stored in your liver and muscles that may be converted to glucose when needed). The key to running at your best is to have enough fuel readily available when it is needed.

Carbohydrate intake that satisfies the general recommendations stated above will provide the blood and liver with enough glucose and glycogen to support moderately high intensity exercise for approximately 60-90 minutes. Thus, longer runs will exhaust these reserves and therefore require more carbohydrates before, during, and after the run. A good daily recommendation for endurance athletes is to consume approximately 7 – 10 grams of carbohydrate for every kilogram of body weight (to calculate kilograms, divide your body weight by 2.2). The table below outlines more specific carbohydrate needs for each type of running athlete.

Exercise Intensity (Distance Example)

Carbohydrates Before Exercise
Carbohydrates During Exercise
Carbohydrates After Exercise

Very High Intensity (5k Run)

<30 minutesNone neededNone neededNone needed

High Intensity (10k Run)

30-90 minutes20-25 grams30-60 grams60-80 grams/hour for 3-4 hours
Moderate to High Intensity (Half Marathon; Marathon)>90 minutes20-50 grams + carbohydrate loading60-80 grams/hour60-80 grams/hour for 3-4 hours
Moderate Intensity (Ironman Triathlon; 140 miles/226 kilometers)>6 hours20-50 grams + carbohydrate loading60-100 grams/hour60-80 grams/hour for 3-4 hours

NOTE: Liquid forms of carbohydrates (such as sport drinks or gels) during exercise are best. These should be consumed gradually in 15 minute intervals over the course of the entire run.

Carbohydrate loading prior to competition may facilitate improved performance by delaying fatigue in distance runners. many methods of carbohydrate loading have been presented. Scientific studies that have compared several methods of loading have concluded that the procedure described in the table below may most effectively balance training and competiton day carbohydrate needs that may facilitate optimal performace.

Carbohydrate Intake
1Taper ExerciseNormal Diet
2Taper ExerciseModerate Carbohydrate Intake
3Taper ExerciseModerate Carbohydrate Intake
4Taper ExerciseModerate Carbohydrate Intake
5Taper ExerciseHigh Carbohydrate Intake
6Taper Exercise or RestHigh Carbohydrate Intake
7Taper Exercise or RestHigh Carbohydrate Intake
8CompetitionReplenish with 60-80 grams/hour for 3-4 hours

NOTE: High Carbohydrate Intake = approximately 400-800 grams or 70-80% of daily calories.

About the Author...

Brian Cook

Dr. Cook obtained his PhD from the Department of Anatomy, Physiology and Kinesiology at the University of Florida. He is a sought after international expert who has taught and published extensively on the relationships among physical activity, health, eating behaviors, and exercise physiology.