The word fasting comes from the root word "fast". To fast is to abstain from eating or avoid certain foods.
Fasting is often used in religious ceremonies, preparations or rituals. The custom of fasting has, at one point or another, been a practice of every major religion.
It should be noted that multiplicities of stupid behaviors, or the fact that they've been done since man could think of fasting, does not make fasting a healthy behavior.
There are many purposes for fasting. In some religions, fasting is used as a means to cleanse sinful deeds from your soul. Fasting is also observed as a mourning ritual in some cultures/religions. More commonly, in religious practice, fasting is used as a preparation for the obtainment of an "enhanced spiritual state."
Seriously, though, those aren't good enough reasons to fast. The only "good reason" to fast is on the advisement of your physician in preparation for diagnostic testing or surgery. Even in those cases, fasting is rarely prescribed beyond approximately six hours (long enough for any food matter to have passed through the stomach. This helps lessen the incidence of the patient vomitting during anesthesia and aspirating food particles into the lungs.
It is argued, by spiritual types, that fasting leads to an enhanced perception of the devine. By depriving the body of food (and sometimes water), it is believed that one is sacrificing earthly needs in an effort to reach higher spiritual connections.
If a deity wants you to reach a higher spiritual plane, why can't he dial direct? Even if you subscribe to the assumption that God created you, he obviously created you to eat. On that assumption, he also gave you the sensation of hunger to guarantee that you would eat. In reality, the human body, through the process of evolution and a mechanism geared toward survival, has encoded "hunger cues" into your physiological profile.
When you skip meals, your stomach muscles kick into action and begin contracting. This is what is known as "hunger pangs". At first, these contractions are limited to the stomach and consist of paristaltic contractions. When deprived of food, these contractions can last for 2-3 minutes. These contractions can be painful! These contractions are instigated by a drop in blood sugar.
Jewish laws order a fast on Yom Kippur, the day of atonement.
Orthodox Jews often order brides and grooms to fast on the day prior to their wedding.
As if the "drop count" wasn't high enough, due to stress and excitement, God is now asking the soon-to-be-wed to not eat, too! Nice God!
Many Christians fast during Lent, the period of forty days that Jesus supposedly fasted in the wildnerss.
Obviously, though, mere humans should not fast for forty days in a row! When you fast for a long period of time, your body goes into a state known as ketosis. Ketosis is the process in which your body burns fat and releases ketones (ketones are highly acidic molecules produced by the body as it burns fat). This is dangerous, as we will find out later...
Muslims fast during Ramadan, the ninth month of their year.
Buddhists, especially, fast to attain a higher sphere of "enlightenment" or spiritual alertness.
During the first stages of ketosis, individuals often feel as if they are more alert and/or able to perform physical tasks better. In reality, this stage is temporary and a dangerous signal that the body is trying to release any and all of it's glucose stores. Your brain requires a continue supply of fresh glucose in order to retain optimal mental accuity. If one wanted to be more "in touch" with a spiritual realm, or even their own body, one SHOULD heed the signals that the body is giving. Long term fasting is completely and totally illogical.
Believers often report that they feel "lighter". They ascribe this purity to the absolution of sins from fasting.
In reality, the believer's body, having depleted fat and taxed the body's glucose stores, has no resorted to cannibalism. Without fat, the body will next attack stored protein to maintain a minimal blood glucose level. This creates a chemical imbalance: the ratio of glucose to insulin is screwed up. During this dangerous state, the following CLINICAL side effects might occur:
General discomfort, uneasiness, or ill feeling (malaise),
Irritability, or even aggression,
Rapid heart rate,
Blurry or double vision,
Why would anyone who has another human's best interests in mind subject another human being to such dangerous side effects?
After several days of fasting, some religious groups believe that one is primed to see/her God.
Unfortunately, such visions are purely the result of the brain's lack of fuel. Individuals suffering from the complete and total starvation often report the following symptoms:
Palpitations, or feeling your heartbeat (heartbeat sensations),
Different size pupils,