Junk food normally assigns to foods that contribute many calories but little nutritional value. Of course, what is considered junk food depends on whom you explore. Some might says pizza is junk food, for example. However I personally do not think so, since it contributes real food with nutrients, like cheese and tomato sauce. Add whole-wheat or part whole-wheat crust, plus veggies as a topping, and I would say pizza completely exits the junk food category. Most junk food falls into the categories of either "snack food" or "fast food." And then there are things like breakfast cereals. They seem innocent enough, but some of them could definitely be considered junk food, as they mostly contain sugar or high-fructose corn syrup and white flour or milled corn.