I am wondering how hydrated you are. How much do you normally drink? Are you a big sweat-er? Do you put anything (like electrolytes) in your water? The electrolytes seem to have a bigger impact on me than eating.
Trek Madone - 5.5 -Brooks B-17
Trek 2.1 WSD - Brooks - B-17 - Trainer bike;
Gary Fisher - Tassajara (MTB) - Specialized Ariel