According to Wikipedia, the term junk food
dates back at least to the early 1950s, although its coinage has been credited to Michael F. Jacobson of the Center for Science in the Public Interest, in 1972. It refers to anything made principally of (1) white flour and or (2) refined white sugar or syrup. For example, white bread, crackers, cake, candy, ice cream soda, chocolate malted, sundaes, sweetened carbonated beverages.
(Cambridge) adds the denotation of speed in preparing this food:
food that is unhealthy but is quick and easy to eat
On the other hand, processed food seems to have a similar negative connotation:
Processed food has had some sort of chemical or industrial treatment in order to cook it, preserve it, or improve its taste or appearance:
- highly processed convenience foods
My question is: Can junk food be used as a synonym of processed food to mean unhealthy food in non-scientific contexts? Do they belong to the same register of language (my feeling is that junk food is less formal)? To be more concrete, can we swap the two expressions in these examples:
I Cut Out Processed Food [Junk Food?] for a Month to Quit My ‘Healthy’ Eating Habits (source)
I do not eat junk foods [processed foods?] or stuff like that during cheat days. (source)
Best Answer
It cannot be used as a synonym; what can be said is that "processed food" can sometimes be not as healthy as other food. This source makes this clear.
It is obvious that the processes are, for the most important ones, those used for a lot of food considered healthy, and that such items as breakfast cereals, sliced bread or cheese can't be called junkfood. The nutritional value of bread products, cheese and cereals is unquestioned.