Nutrition is the foundation for your health, fitness, and performance. If we had to choose between nutrition or training for our athletes' overall health, we would choose nutrition. However, training and nutrition cannot be separated. In CrossFit founder Greg Glassman's description of fitness, he begins with food: "Eat meat and vegetables, nuts and seeds, some fruit, little starch and no sugar. Keep intake to levels that will support exercise but not body fat."
Training sends the signal for your body to adapt, and nutrition provides the building blocks for those adaptations. Without the fuel, you will not see change. If you are looking to get the largest return on your investment from training, nutrition is the ticket. Focusing on this will move the needle more than anything else you can do for your results.