There are many proponents of fasting.
And as with many other diets, there are people who have had massive benefits from it.
Your mileage WILL vary!
We know so little about nutrition, and worse, most of what we think we know has actually been govern-cement lying.
The number one thing fasting seems to do is clean out the gut and allow it to rejuvenate. But, we have finally started thinking in terms of gut biome and it being essential, as opposed to a bunch of things that shouldn't be there, and so we are still a ways off from anything our future selves will call nutrition.