Courtesy of CrossFit HQ
The CrossFit dietary prescription is as follows:
Protein should be lean and varied and account for about 30% of your total caloric load.
Carbohydrates should be predominantly low-glycemic and account for about 40% of your total caloric load.
Fat should be predominantly monounsaturated and account for about 30% of your total caloric load.
What Should I Eat?
In plain language, base your diet on garden vegetables, especially greens, lean meats, nuts and seeds, little starch, and no sugar. That's about as simple as we can get. Many have observed that keeping your grocery cart to the perimeter of the grocery store while avoiding the aisles is a great way to protect your health. Food is perishable. The stuff with long shelf life is all suspect. If you follow these simple guidelines you will benefit from nearly all that can be achieved through nutrition.
What Foods Should I Avoid?
Excessive consumption of high-glycemic carbohydrates is the primary culprit in nutritionally caused health problems. High glycemic carbohydrates are those that raise blood sugar too rapidly. They include rice, bread, candy, potato, sweets, sodas, and most processed carbohydrates. Processing can include bleaching, baking, grinding, and refining. Processing of carbohydrates greatly increases their glycemic index a measure of their propensity to elevate blood sugar.
Caloric Restriction and Longevity...
Current research strongly supports the link between caloric restriction and an increased life expectancy. The incidence of cancers and heart disease sharply decline with a diet that is carefully limited in controlling caloric intake. "Caloric Restriction" is another fruitful area for Internet search. The CrossFit prescription is consistent with this research. The CrossFit prescription allows a reduced caloric intake and yet still provides ample nutrition for rigorous activity.
For more info on Nutrition you can read more here. Good Food, Bad Food