My wife's uncle ran many a decent marathon - about 13-15 in the 2:29.00 - 2:34.00 range. After talking to him in detail about his training; he would only back off his training on Wednesday if the marathon was on Saturday/Sunday; he stated that he at a fair more amount of protein - in the form of long john silvers chicken/fish. He sometimes even raced the day before a marathon - one time clocking his best 10k the day before. He raced frequently and most of his running was an 1 hour in the morning and 2 hours in the evening with a few bursts here and there. Pretty simple running really.
Nick