I’m going to be That Guy™ who jumps in and says cutting out carbs isn’t a fad diet. Doctors have experimented with keto diets to treat various health issues since the 1930s, and it clearly brings results, not even just weight loss. It’s silly to make the claim that just because something is popular, it should be avoided as a “fad diet”. Do the research, read arguments from both sides of a debate, and make your own decision.
That said, there is a lot of research supporting the Mediterranean diet.