The importance of carbohydrates (CHO) as a fuel source for endurance exercise and athletic performance is well established. However, carbohydrate dietary recommendations for endurance athletes must continually evolve to reflect current knowledge and practice, with optimal health and performance outcomes in mind. From Olympians to amateur exercisers, athletes of all levels face the same questions—what should I eat before exercise and how does it affect my training?
Duration and intensity of exercise are the most important factors influencing the response to endurance training, however changing nutrient availability before and during exercise can also affect the training response1.
Most endurance athletes are familiar with high-carbohydrate diets, as they have been tested for a long time and continue to be recommended in endurance events1. The exact calculation of the ideal amounts, however, requires an analytical mathematical calculation, as it is necessary to take into account the duration and intensity of the exercise as well as the athlete’s physical characteristics.
Daily CHO requirements vary depending on exercise level, with recommendations so far being as follows:
- 5–7 g/kg body weight for athletes exercising at moderate intensity for about 1 hour per day
- 6–10 g/kg body weight for athletes 1–3 hours per day
- up to 8-12 g/kg/day for athletes who exercise more than 4 hours a day.
Pre-race recommendations (“loading”) also vary depending on the duration of the exercise.
- from 6 g/kg/day (<90 minutes of exercise)
- 10–12 g/kg/day (>90 minutes of exercise)
1-4 g/kg final top-off 1-4 hours before the race.
During the race (“Fueling”) the requirements vary similarly:
- from 30-60 g/hour for <2.5 hours of exercise
- 60-70 g/h for >2.5 hours of exercise
- up to 90 g/h for >2.5 hours of exercise if tolerated
Overall, the importance of pre-exercise CHO consumption increases as the duration of exercise increases1,2.
After the exercise the recommendations are:
- 8–10 g/kg/day (first 24 hours)
- 1.0–1.2 g/kg/hour (first 3–5 hours) or 0.8 g/kg/hour + protein (0.3 mg/kg/hour) or caffeine (3 mg/kg)
As daily requirements, pre-exercise, during and post-exercise requirements are scaled to exercise level and can be confusing to the athlete, it is important to at least emphasize that the size and timing of carbohydrate meals have no such a great effect on the performance of the athlete compared to exercising without having consumed a meal, i.e. after fasting (fasting).2In sports medicine centers of the U.S. a study comparing the results of endurance training after an overnight fast and after a carbohydrate-rich breakfast was carried out. Participants were >>80% trained men aged between 20-30 years, and performance has been shown to improve after consuming CHO prior to longer duration exercise2.
In any case, carbohydrate consumption seems to contribute positively to endurance performance, so depending on the athletic demands and the level of the athlete, one can if desired calculate the ideal amounts of CHO to approach the strength-optimal amount.
- Vitale, K.; Getzin, A. Nutrition and Supplement Update for the Endurance Athlete: Review and Recommendations. Nutrients 2019, 11, 1289. https://doi.org/10.3390/nu11061289
- Rothschild JA, Kilding AE, Plews DJ. What Should I Eat before Exercise? Pre-Exercise Nutrition and the Response to Endurance Exercise: Current Prospective and Future Directions. Nutrients. 2020 Nov 12;12(11):3473. doi: 10.3390/nu12113473. PMID: 33198277; PMCID: PMC7696145.
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