Glycogen is the primary source fuel for exercise. To increase glycogen levels, eat complex carbohydrates such as whole-grain wheat pasta and rice. High-quality protein sources include fish and chicken. Keep an eye on labels. Avoid processed and refined foods.
Salt is the leading cause of dehydration for most marathoners.
Avoid restaurant food. If you're having trouble taking in enough carbohydrates, try high carbohydrate supplements such as Gatorlode. On race day, set your alarm clock to wake up in plenty of time to go through the eating and drinking time table which worked for you before your training long runs. The foods and the pattern of eating that worked for you during your training long runs will work for the marathon. While many people find supplements such as sports bars digest most quickly and provide the best blood sugar stabilizing effects, go with what works best for you.