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The traditional pasta meal the night before a long distance event is not actually carbo loading. Carbo loading is a process that takes several days, and involves increasing carbohydrate intake while tapering exercise.
Note: Studies have shown that the traditional carbohydrate depletion phase, during which the athlete significantly reduces carbohydrate intake, doesn't improve carbohydrate storage in the muscles meaningfully, but can lead to headaches, fatigue and other health problems.
Endurance athletes engaged in vigorous exercise for less than 90 minutes don't benefit significantly from carbo loading, but marathoners, triathletes and others engaged in longer endurance exercise can. This is because your muscles and liver normally only store about enough carbohydrates to carry your body the equivalent of about 20 miles of running. (Now you know why marathoners hit “the wall.”)
During the week prior to the event, carbo loading involves tapering exercise (don't stop altogether!) and increasing carbohydrate intake to about 70% of total calories. (Reduce fat intake to balance total calories consumed.) This process supersaturates the muscles with carbohydrates – up to nearly twice their normal capacity.