This article is from the Misc Bicycles FAQs, by various authors.
The only way to be sure you're eating well is to do a dietary
analysis. Estimating just doesn't cut it. Write down your standard
diet for three days. Specify the quantities and descriptions of all
meals and snacks. Then: 1) Check out a copy of the "Nutritive Values
of American Foods" and look up the nutritive values of what you ate.
Or, 2) Take your diet list to a Registered Dietitian for a detailed
computer analysis. This is about the most useful information an
athlete can get.
For the definitive word on nutrition go to the nearest college
bookstore and pick up a copy of "Nutrition for Living" (Christian, J.,
Benjamin/Cummings, 1985). This volume serves as the reference text for
most nutrition courses. It is well written and informative without the
biases and inaccuracies often found in popular books.