Meat, vegetables, nuts and seeds, some fruit, little starch and no sugar is the prescribed diet by CrossFit.
Two great diet plans that we support and endorse are the Zone Diet (http://www.zonediet.com/) and the Paleo diet (http://thepaleodiet.com/). These diets are fantastic for muscle building, weightloss and all around health. For more information, their respective websites explain it best. If you have any questions, of course do not be afraid to ask!
At CrossFit Moorabbin, we offer all of our clients all of the nutritional assistance that they want. These diets are not something we enforce, but anyone that wants help has 100% access to it. We are committed to helping you reach your goals.