saw some kraft fat-free swiss cheese in the grocery the other day. 60 calories per slice -- is this still terrible for you, if you have a slice a day with a turkey sandwich?

Well, if there is no fat then the 60 calories are either from sugar (likely) or protein (probably some).

at 4 Calories a pop you are looking at 15g of Carbs or 15g of protein, or some mix of the two.

At 60 calories a serving, in my opinion it won't blow a diet (unless it is 15g of carbs and you are on a keto / atkins / southbeach type diet)

Obviously it has fewer Calories then non-fatfree cheese.