It is usually less healthy when you use any diet to reduce weight. Only when your body suffers from conditions that demand a diet it is helpful. Given that in western countries especially people are used to and it is a custom to basically have unhealthy eating habits, going back to a well balanced food is a good thing. But calling that a diet is wrong. Any extreme forms of diets that promote to normal people exaggerated intake of single forms of food are unhealthy after a short while. While there may exist medical conditions that require to do so for a limited time in a controlled way there can ony be damage be expected when doing so as a healthy person following the counsel of people who want to sell a cult or products.