Could depression or other psychiatric condition cause a 180 reversal in palate, i.e. cause a lifelong healthy eater to crave fatty fast foods?

Depression, appetite: Depression is well known to impact appetite, eating either less or more than normally. Pharmaceuticals used for depression can do this also -- often resulting in weight gain. Review these issues with your own physician. You could also consult a homeopathic psychiatrist trained to consider such changes comprehensively, because peculiarities like this can help find an effective remedy for you.

Yes: Many people suffering depression turn to "comfort foods" for temporary relief. This can consist of overeating fatty or sweet foods (cookies, ice cream, etc). Although appetite & eventually weight usually go down with depression, the opposite is not uncommon: sometimes food intake and weight increase instead. Other conditions such as anxiety and mania can also (less often) affect food choices.