When preparing for a marathon or long-distance race event, nutrition can certainly be a limiting factor. Muscle glycogen is the primary fuel athletes use in training and racing. Carbohydrate loading (the infamous, “carbo-load”) strategy has been shown to enhance marathon and long-distance performance by preventing premature fatigue.
Sports nutritionists recommend that endurance athletes consume adequate carbohydrates to promote restoration of muscle glycogen between training sessions, for ideal recovery. Basically-make sure you are eating carbohydrates between workouts for recovery as well as to fuel your next workout. In general, endurance athletes should be sure that 60-65% of their daily calories come from high-quality carbohydrate sources, 12-15% from protein, and 25-30% from fat.
For a marathon (or longer) event, the last meal should be completed at least 3 hours before the start of the race to ensure that timing of energy release is ideal, and to avoid any gastro-intestinal problems. Foods that are rich in carbohydrates (bread, oatmeal, cereals, pasta, rice, potatoes) However, some easily digestible fat and protein sources are also needed to help the carbohydrates supply a steady release of energy to the blood. A good example would be a bagel with nutbutter or oatmeal with nuts or butter, or nutbutter, giving you the carbohydrates and fat source.
Keep in mind, however, it is important to be able to supply adequate amounts of high quality foods without causing disturbances to the gastrointestinal (GI) tract. A pre-competition meal should not stray from foods that you normally eat in your everyday habitual diet.
Carbohydrate drinks have been loved and hated throughout the years. One camp claims that sports drinks before a race cause insulin to spike, and then drop during the race causing a “crash”. Studies more recently show these shifts in blood glucose are to minimal to cause a problem.
Hydration is of special concern for athletes who are exercising for extended periods of time. It’s not uncommon to forget to hydrate when training and racing, however, it is very important to have a hydration strategy in place prior to a race event and to practice regular and consistent hydration while training.
Be careful not to exceed ~700-800 ml per hour during a marathon, as high volumes have been shown to present intolerance problems. It is key to have a hydration strategy to consume ~150-200 ml periodically throughout the race. If you know the course beforehand, look at the sections of the race profile where you can take a drink effortlessly.