In fasting, the body undergoes a series of hormonal and metabolic changes to conserve its body mass and draw selectively from its supply of energy in adipose tissue, sparing the breakdown of muscles or enzymes. By the third day of a fast, the liver begins generating large quantities of ketones which are a fat breakdown product that many cells can use as an alternative (emergency) fuel rather than carbohydrates. As ketone production increases, a condition called ketosis occurs and the acids rise in our bloodstream. Ketosis develops within 48 hours in fasting females and 72 hours in males and can be measured by checking the acidity of urine samples.

 

As the level of ketones rises in the bloodstream, they compete with glucose as a substance that can be used for energy in the central nervous system, thereby greatly diminishing the body’s need for glucose, sparing protein, and preventing further acidosis caused by tissue catabolism. Through this inherent survival mechanism, the brain, muscle and heart begin to use ketones instead of glucose as fuel. Muscle wasting at this time decreases to less than 0.2 kg per day - this is known as protein sparing. In this phase, muscle is conserved and the maximum breakdown of fatty tissue and removal of atheromas and toxins occur.

 

The unique nutritional adjustments that occur during a total fast, including the adaptation to ketone nutrition, apparently have long-term beneficial effects on brain function, improving psychological health as well as physical well-being. When EEG (electroencephalogram) data and endocrine parameters are measured during and after fasting, it appears the homeostasis mechanism of the body significantly improves in the central nervous syste