most athletes who practice crossfit singularly eat what Is known as the Paleolithic diet, which consists of meat, vegetables, nuts and a small amount of fruit. processed foods an breads are completely eliminated or reduced drastically so as to keep gluten an sugars out of the body. many crossfit athletes also have adapted their bodies to training on no food or very small amount of food so as not to impede their metabolism during metcon workouts. I have found that the majority of my personal best times doing crossfit workout have occurred on an empty stomach or when I have ingested a small protein drink along w 8 oz black coffee.