Yes, while I'm fasting, many of my health symptoms improve which is why I would do it. But always, when I came back from a fast, I would be in a worse position that I started. Worse tolerance to food, weaker. But I was underweight when I started and now I'm badly underweight. I also have several medical conditions including Hashimotos so maybe I shouldn't generalise. Nevertheless, I won't fast again.
With regard to diets, it is a bit of a mystery as to what is the best. Definitely the best way to eat well is to increase your intake of vegetables and decrease your intake of starchy and refined carbs a lot