This does not mean going without food. Fasting is to be simple and nutritious at the same time.
Starving the body may create deficiencies. The human body is not designed to go without.
We don't stop putting petrol into the car to give it a clean out. You put new petrol that is clean into the car. 
The body requires the same thing. If you put clean food into the body it will clean itself. The body requires the replacement of minerals and protein and carbohydrates that the body uses up during the course of the day. We do not store protein and it must be replaced daily. One way to fast is the following:
Carrot, Onion, Wakame Miso Soup
Brown Rice
Bancha Tea. This has no caffeine and very low tannin.
The above food is a combination of minerals, vitamins, proteins and carbohydrates. These foods may be consumed in any amount at any time of the day or night. This combination is very beneficial for 3 days. We do not need to continue any longer unless under the guidance of a health professional. The body will feel lighter and cleaner after 3 days.
The key is only in the spring time.
