Hello and welcome to HCM, Fasting leads to many metabolic changes in the body. Initially there is depletion of glycogen stores in the body to release glucose. When glycogen stores are depleted, the fat stores are used up. The fat is burned or metabolized to release glucose. When the fat stores are also depleted, the protein stores are metabolized. Proteins are building blocks of the body required for repair and regeneration. The protein stores are used for providing energy instead of their normal function of repair and regeneration. When fats and amino acids (smallest units of proteins) are used up, there is release of ketone bodies in blood. This leads to ketosis and ketonuria. When large amounts of ketone bodies are accumulated in blood, patient can land up in coma. It is this metabolic change which can cause death, the duration varies from person to person. In addition, no fluid intake will speeden up ketosis due to dehydration. Thus, starvation does not have any beneficial affect on body if carried out for long durations. Thanks and take care Dr Shailja P Wahal