Is there an official specific Mediterranean diet? Is it the Mediterranean of Spain, Italy, Greece, Turkey, Lebanon, or Egypt, etc.? And from what era/period, because my understanding is that those places are seeing significant increases in chronic metabolic disease as well.

From what I've read, Mediterranean means something sorta along the lines of "natural whole foods, not much meat, lots of olive oil nuts and salads" -- and this is vague nutrition advice which can apply to almost any non-exclusionary diet.