You just made an excellent point about something I observed many years ago; many fad diets merely relieve the symptoms, but as soon as they get off the diet, the symptoms come back. Why? Because diet alone does not give the specifically needed nutrients the body needs to heal itself.
Diets can be nothing more than allopathic [symptomatic relief]. (side point - I think I use the word allopathic wrongly. But in this context, it means symptomatic relief.)