The importance of ingesting carbohydrates to prepare for marathons cannot be overstated. Though carbohydrate ingestion does not typically help a runner run a faster time during his or her race, it does help him or her maintain the self-selected running speed over long distances.
Runners often practice the strategy of carbohydrate loading as they prepare for their races. The typical carbohydrate loading strategy is as follows: a runner will taper off of his or her training regimen and begin consuming greater amounts of carbohydrate per kilogram of his or her body weight each day leading up to the race only after reducing carbohydrate intake for two to five days prior. This is known as the Depletion/Replenish Cycle.
Another carbohydrate loading strategy is also frequently used. In this instance, a runner will simply increase his or her carbohydrate consumption without first reducing carbohydrate intake. This is known as the Super-Compensation Strategy. No matter which strategy a runner chooses to adopt, it is recommended that runners ingest carbohydrates after each training session and especially after races in order to help restore the glycogen levels in the body.
There is relatively little difference between the storage capacities of men and those of women, provided both genders ingest the necessary amount to maintain body weight and adequately train for the race. That is why researchers do not typically give separate recommendation numbers for men and women. Furthermore, it is not recommended that marathon runners ever decrease their carbohydrate intake the last few days prior to the race. Some runners in the past have tried that strategy in attempts to increase their use of body fat (fat oxidation) as energy for their races. It didn't turn out well for those runners. Generally, the recommendation for carbohydrate intake in the days leading up to a marathon is as follows: ten to twelve grams of carbohydrate per kilogram of body per day in the days leading up to the event.
Ensuring adequate nutritional intake is a key aspect of training for a marathon. Many factors must be considered regarding the proper intake, some of which are carbohydrate intake (type, amount, and timing), tapering (when and to what extent), exercise load per day, fluid consumption (type, amount, and timing), the age and health of the runner, and the climate in which the runner is training.
In considering children, they should, with careful supervision of an adult and a nutritionist or dietician, increase their carbohydrate intake as they train above and beyond the recommended amounts for adults. Doing so will likely enable the child to maintain normal growth and development rates. This may also help to offset burnout and prevent injury.
Stellingwerff, T. (2012). Case Study: Nutrition and Training Periodization in Three Elite Marathon Runners. International Journal of Sport Nutrition and Exercise Metabolism, 22, 392-400.