I think the word "addiction" gets thrown around entirely too much.
But it's well known that a lot of processed foods contain chemicals that are designed to attract the senses extremely powerfully, and also that they are designed to reduce satiety (i.e., you can keep eating them without feeling full). If you've been eating that cr*p your entire life, it is challenging to retrain your palate.
Heck, even though I've eaten reasonably well most of my life, almost never had fast food or anything processed as a child, it was a challenge to learn to eat salads with no dressing when I came up allergic to molds (and eliminated vinegar as well as other mold-containing foods from my diet). When the real flavor of food is completely hidden by chemicals (natural or synthetic) that appeal to the senses, it really takes some effort to learn to appreciate the flavor of a leaf of lettuce, or arugula, or baby mustard, or baby pac choi. (Especially if it's at an inexpensive grocery or restaurant and the vegetables are neither very good quality nor very fresh.)
Speed comes from what you put behind you. - Judi Ketteler