There is a reason why it is called junk. The calories are of the lowest quality and filled with fat and sugar. High-fat foods tend to blunt your appetite for hours and you stop eating on schedule and fail to keep a steady flow of aminos heading into your muscles. In order to maximise absorption for optimal mass gain, you need to eat smaller and more frequent meals of quality calories. Five thousand calories in one sitting does not equal 5,000 calories spread throughout the day.
Never eat too much junk food when trying to add muscle mass, because extra fat will be gained. Some junk foods is allowable once a week, but remember “You are what you eat”. So eat healthy, nutritious, low-fat bodybuilding foods.