This is really interesting because it is stated in the bible that Jesus pasted for fourty days and nights to strenghten his self. because of that action most of our great seekers and sages like Buddha; Mahatma Gandhi; Dalai lama and others doing the same thing.
That might be the reason they are so discipline in anything. according to the scriptures that Fasting is often associated with prayer. In Ezra 8:15-36 one can read of an account where there was a request made for God to grant a safe journey and the people not only prayed to God they also refrained from eating for an allotted duration.fasting
further, Matthew 6:16-18 says, “when you fast, do not look gloomy like the hypocrites, for they disfigure their faces that their fasting may be seen by others. Truly, I say to you, they have received their reward. But when you fast, anoint your head and wash your face, that your fasting may not be seen by others but by your Father who is in secret. And your Father who sees in secret will reward you.” The thrust of verses 16-18 is that God will know the situation of the one who is choosing to fast; and thus, there should be no reason to act gloomy, or walk around in sorrow, but rather to “wash up” and not appear to the world to be fasting.
On the other hand, The process of ketosis is one of the physiological effects of fasting in which the brain (and some other bodily processes) uses ketones produced from fatty tissues as a fuel instead of the usual glucose. This is called “muscle sparing”.
When glucose isn’t readily available via the diet (in the form of carbohydrates) and the glycogen stores in the liver become depleted, the body could break down muscle to get it. But ketosis is an adaptation that will spare muscle during times of shortage by instead breaking down fat stores and manufacturing ketones for brain fuel. It is said this state is attained at approximately 48 hours of a water fast for women and closer to 72 hours for men.
The effects of fasting ketosis have become a more popular and controversial subject in recent years due to low-carb, high-protein dieters relying on it long-term to “burn the fat”.
Where ketosis was once considered a “crisis response” of the body and fine only for short durations, there are some doctors who now contend ketones are an acceptable alternative fuel, produced and used by the body any time glucose is scarce, which can happen even in non-fasting, non-dieting individuals, such as during intense exercise or during sleep. They are considering it a natural metabolic process where ketone production and use fluctuates constantly in response to the body’s needs.
What is so controversial about the low-carbers use of ketosis is the long term, artificially produced, use of it. Over long periods of time, their high-protein diet produces excess protein by-products that become a strain on the kidneys to eliminate. Ketosis also creates a mild acidosis of the blood, which, over a long period of time is considered detrimental to our health. One effect being the leaching of minerals from our bones, causing osteoporosis.