Many people look at it as a tool for weight loss or referring it to as 80% nutrition and 20% training. I honestly believe it takes 100% commitment to a lifestyle change.
Muscle is built and fat is torched by your training, so unless you're fueled up and recovering with a well balanced nutrition plan than your training will always suffer.
Cheat meals are also vital for strength and metabolic progress. All of my clients including myself have a real cheat meal once a week.