I suscribe to the idea that if a caveman wouldn't eat it then dont eat it. Everything is fair game. Meats, vegetables, nuts, seeds, and a little bit of fruit. Thats the crossfit prescription. Mark ripptoe will tell you to drink milk and drink lots of it. Up to a gallon a day if your trying to make strength gains. Personally I committed to eating 5 ounces of meat, and two vegetables every meal. I do a small handfull of nuts and a piece of fruit inbetween. I've been doing that since November of last year. When I started could barely do a pullup or much of anything else after an injury. My fitness levels are jumping considerably since then. I can do 10 pullups very comfortably now and although haven't maxed am sure I could do 15. Pushups and squats have also gone up by leaps and bounds.
Not as important for me really but was about 208 lbs when I began and weighed in at 178 today. My wife says my arms are much bigger. Again not as important but you get the idea.