Fad, extreme diets are what gives nutrition a bad name. Most traditional diets like the Japanese or the Mediterranean diets are healthy, common sense diets (high fruit and vegetable intakes, lots of nuts, seafood, leguminous, greens and varied diets with lower meat content and few processed foods) and the people who practice them are healthy people. More often than not the food is great as well, you don't have to deprive yourself too much to eat well.
“Nothing is more useful than to look upon the world as it really is.”