For any zen practice, it is key to master fasting. Fasting is a process of not eating for a duration of time. Through practice, it removes urges within the body. The urges are of various kinds. It really depends what kind of food we eat every day. Various urges within the body are associated with that type of food. Through fasting, we are able to distinguish each type of urge. The other important factor of fasting is devotion. Many people in the world fast for a prayer in mind. It is the ultimate form of Bhakti yoga. Surrender Self for the greater good. This creates harmony within the body. When we fast for a duration, and then eat, the food tastes much better. The body takes a break from regular operation. A new paradigm opens. Once we get better at fasting, then we can extend the duration of the fast. For example, a native american vision quest requires 4 days of no food and water. The body has to be prepared for this rigorous exercise. Depending on our eating habits, the urges could take over the body and the person might collapse. However, only to wake up and find that something drastic has changed in their lives, from that point on. Fasting is a powerful tool for awakening, or higher human consciousness. When I lived with the zen master, he associated urges to amoeba within the body. Amoeba are of various forms, and they are physical worms that feed on the food within the body. When a person dies, it's the amoeba that eat the body from the inside. Hence by fasting, we are able to remove food urges and move to a healthier diet.