I don’t doubt that some intermittent fasting might be beneficial, after all, most of us do it every night.
But the extreme fasts that are often promoted are just silly. Three days without eating is insane.
I do a three-day fast once a month. Frankly, I have to remind myself to eat by the end of it, I’m not even thinking about food.
I should elaborate however, that it’s something you do have to work up to. You have to go on a low-carb diet, and then gradually increase your daily fasting periods.