What exactly is junk food?
Some things are obvious ... Soda, candy bars, donuts, etc.
And some things are obviously not junk food ... fruits, vegetables, etc.
But between those two poles is a vast murky middle ground, right?
Take candy bars for example. You say a Snickers bar is junk, but what about a Snickers Dark, which is made out of dark chocolate. Dark chocolate is supposed to have anti-oxidant and other healthful benefits. And, aren't peanuts good for you, which all Snickers bars have? Junk?
And what about something benign like rice cakes. They certainly aren't harmful in the sense that they are full of transfats or high in sodium or sugar, but then they are essentially empty calories -- offering only simple carbs and very little fiber. Junk? If cardboard had calories, we would just call them rice cakes and make the dictionary one word less voluminous.
Or, how about cheese pizza? Cheese is high in calcium and protein. Tomato sauce is high in anti-oxidants and vitamins and minerals. Is the problem that the crust may be made from white flour? What if it was a whole-wheat crust? Still junk?