A real fast, i.e., just water for 24-36 hours is a good thing. So is IFing for 18 hours per day. Choose whatever fits into your lifestyle.
There's also 5:2 - eat what you want for five days, and eat fewer than 500 calories two days a week. I like this because it's do-able for the rest of one's life.
There's also upday/downday. Also something that can be done forever.
I think various fasting methods are good both physically and mentally.
"Right is right, even if no one is doing it; wrong is wrong, even if everyone is doing it." - St. Augustine