Understanding the Fast

From: http://www.healthpromoting.com/Articles/articles/therap.htm

The physiology of fasting has been extensively studied, and three phases of fasting have been identified.

The first phase can be called the gastrointestinal phase, and lasts approximately for first six hours following the last meal. During this phase the body uses glucose, amino acids and fats, as they are absorbed from the intestinal tract.

Phase two lasts for more or less the next two days. During this time the body will use its glycogen (sugar) reserves that are stored in the muscle and liver cells. These glycogen reserves are mobilized to provide the central nervous system, including the brain, with its normal fuel, glucose. Within a few hours the body begins to convert adipose (fat) tissue into fatty acids.

Were it not for the body’s ability to switch fuels and enter phase three, where the body switches from glucose to fat metabolism, therapeutic fasting could not take place. The body’s protein reserves would be quickly depleted.

Fortunately, this is not a problem. In fact, within ten hours from the last meal approximately 50% of muscle fuel is coming from fat. Even the brain itself begins to shift over the fat metabolism. The consumption of protein reserves decreases from 75 grams per day at the beginning of a fast to just 20 grams a day by the end of the second week.

As you can see, excess activity including excess emotional stress could increase the body’s fuel needs, interfering with the optimum adaptation to the fasting state.

Body reserves differ from individual to individual. But a “typical” 155-pound male at normal weight has enough reserves to fast for between two to four months. If the fast were allowed to continue beyond the individual’s reserves, starvation would ensue and serious damage and eventually death would occur.