Part 2 of Coach Glassman's discussion of nutrition addresses the refined dietary needs of athletes and what's required to optimize your performance. If you want elite physical output, you must be precise about your intake. "Close enough" won't cut it--or as Coach Glassman more colorfully puts it, "If you want top-fuel- type performance, you need top fuel; you can't just piss into the gas tank."
Most of us are familiar with CrossFit's nutrition prescription: Eat meat and vegetables, nuts and seeds, some fruit, little starch, and no sugar. But to achieve top performance, you have to be specific about the balances of those things and accurate in your macronutrient consumption. You can get far on the workouts alone, but you will not--cannot--reach your true potential without getting particular about your fuel. There's a 1:1 correspondence between elite CrossFit performance and accuracy and precision in your consumption. For more information on getting specific about your intake, see the following resources:
CrossFit Journal # 15 is an annotated reference list of books on nutrition that could keep you reading as long as your heart desires.
CrossFit Journal #21 goes into detail about how to determine how much of what you should be eating to optimize your performance.
Greg Glassman is the founder (with Lauren Glassman) of CrossFit, Inc. and CrossFit Santa Cruz.