I heard a really great phrase today: "You CANNOT out-exercise a lousy diet." Beleive me, it's impossible. I've watched lots of people try to do it. You can workout until you're blue in the face, but if you're not eating to support your body and its activities, you will not reach your goals. Period.
Every meal you eat should consist of a lean protein, a fibrous carbohydrate, and a healthy fat. Starchy carbs can be added in at times as well. Let's focus on the first three.