Fasting is the opposite of eating. So, if you really want to fast, you will go for a period of time where you don’t eat. That period can be 16 hours, 18 hours, 20, etc. However long you want it to be. The longer the better, but some folks find they have to work their way up to 24 hours plus.Start by skipping either breakfast or dinner and gradually extend fasting window.Drink plenty of water and if you go beyond 24 hours, you may want to supplement electrolytes (salt and potassium for sure).