According to the BBC Inside Health podcast I recently listened to they are often bad for you because the processing removes fibre and vitamins and also makes sugars more available. And that to make them int4eresting enough to eat excess salt is added.

This strikes at a problem with the definition of "processing" foods. Nixtamalization is "processing," but is mandatory to ensure one does not develop a vitamin deficiency on a maize diet.

WHO says "eat 30 grams of fibre every day". Which is a lot, unless you use whole grains without sweeteners, fat or meat on top (which reduces fibre per calorie). Or eat lots of roots or cabbage, and salads. Especially since you have to think of eating until 30 grams of pure fibre content is reached every. Single. Day. Of. A. Year.