Actually there is no such thing as a junk diet or clean diet, but people including me like to use this term to clarify what types of food they will be eating. FOOD IS FOOD! Now, as far as I'm concerned sugar for example is not food so when someone says that they are going to eat a Kit Kat then that would classify as partial food and the rest non food as in junk ie chemicals food dyes sugar etc. Anytime you put something in your body that gives you no nutritional value could be classified as "junk".