This article is from the Alternative Medicine Therapies guide.
Critics of fasting therapy often confuse fasting with starvation. In the fasting state, nonessential tissue, like fat, is used for fuel while vital organs are spared. Starvation occurs when the body has depleted its fat stores and begins to use vital organs for fuel. Obviously, if the body does not receive food after a supervised fast, starvation and death will inevitably follow.
The series of physiologic events that occurs within the body during a fasting state has been well-studied and follows a definite sequence. Basically, the body undergoes certain changes in metabolism to conserve its energy sources but continues to function with the same degree of efficiency. For example, blood sugar levels remain fairly constant no matter how long the fast lasts.
Early in fasting, the body both manufactures glucose (gluconeogenesis) and releases stores of it from within the liver (glycogenolysis). After a few days, the body will release triglycerides from fat cells. These tryglycerides become oxidized and form acids called ketones, which are then used for energy production. All of these changes slow the overall metabolism of the body to about 75% of its normal rate. For this reason, plenty of rest (and no vigorous exercise) is routinely advised while fasting.