You should keep constantly monitoring your results
. If you notice you are gaining fat then you need to make changes in your diet. You also need to keep up with the exercising, doing both cardiovascular exercises and weight lifting. You want to watch everyday for changes that show signs of fat gain instead of muscle gain. You may need to make adjustments regularly, but eventually you should find the perfect eating plan that works for your body. From that point on you should have no issues with eating to build muscle mass.