Mattson points out that, from an evolutionary perspective, the brain power that fasting generates makes sense. Mammals typically go days without food, often hunting on an empty belly. Semi-starved animals with enhanced smarts and energy would be more likely to obtain food and live another day. “If you are that wolf or lion, now a week with no food, you better be able to focus your mind and concentrate on what you need to do to get food,” he says.
Refraining from eating food. The Bible describes three main forms of fasting: 1) The Normal Fast, involving the total abstinence of food. Luke 4:2 reveals that Jesus "did eat nothing." Afterwards "He was hungered." Jesus abstained from food but not from water. 2) In Acts 9:9 we read of an Absolute Fast where for three days He "neither did eat nor drink." The abstinence from both food and water seems to have lasted no more than three days (Ezra 10:6; Esther 4:16). 3) The Partial Fast-in Daniel 10:3 the emphasis is upon the restriction of diet rather than complete abstinence. The context implies that there were physical benefits resulting from this partial fast. However, this verse indicates that there was a revelation given to Daniel as a result of this time of fasting.
Weight-loss resistance can often be due to an underlying hormone imbalance. Leptin resistance occurs when your brain stops recognizing leptin's signals to use your body’s fat stores for energy. This causes your body to continually store fat instead of using it. Intermittent fasting has been shown to improve chronic inflammation that can dull the brain’s leptin receptor sites.
You'll probably lose weight on the Fast Diet because you’ll consume significantly fewer calories than you normally would on two days of the week. If you actually stick with the plan, you'll steadily drop weight. And because the two fast days are nonconsecutive and allow for at least some eating, the diet authors have found that people don't typically binge and overeat on the nonfasting days.
Yes, you'll be hungry at times—but it's not necessarily overwhelming or constant. "Hunger doesn't seem to get worse as the day goes on, and some of our studies report increased fullness and satisfaction," says Kristin Hoddy, Ph.D., R.D.N., a dietitian in private practice who has researched fasting. "Some subjects remarked that they'd get distracted and 'forget' they were hungry."
Hoddy suggests trying a plan for two weeks and keeping a record of how you feel and what you eat. You can switch to another one if it's making you grumpy, or you can modify it; when Hoddy fasted, she split one meal into two smaller ones on fast days so she could have dinner with her husband. Or follow a plan partway, says Peterson. "Any form of fasting helps burn fat, and extending your overnight fast a little—say, eating dinner earlier—is an overall health benefit."
Classical Pentecostalism does not have set days of abstinence and lent, but individuals in the movement may feel they are being directed by the Holy Spirit to undertake either short or extended fasts. Although Pentecostalism has not classified different types of fasting, certain writers within the movement have done so. Arthur Wallis writes about the "Normal Fast" in which pure water alone is consumed. The "Black Fast" in which nothing, not even water, is consumed is also mentioned. Dr. Curtis Ward points out that undertaking a black fast beyond three days may lead to dehydration, may irreparably damage the kidneys, and result in possible death. He further notes that nowhere in the New Testament is it recorded that anyone ever undertook a black fast beyond three days and that one should follow this biblical guideline. Dr. Herbert Shelton advises that one should drink water according to natural thirst. In addition to the Normal Fast and the Black Fast, some undertake what is referred to as the Daniel Fast (or Partial Fast) in which only one type of food (e.g., fruit or fruit and non-starchy vegetables) is consumed. In a Daniel Fast, meat is almost always avoided, in following the example of Daniel and his friends' refusal to eat the meat of Gentiles, which had been offered to idols and not slaughtered in a kosher manner. In some circles of Pentecostals, the term "fast" is simply used, and the decision to drink water is determined on an individual basis. In other circles profuse amounts of pure water is advised to be consumed during the fasting period to aid the cleansing of internal toxins. Most Pentecostal writers on fasting concur with Dr. Mark Mattson who says that sensible intermittent fasting with a sensible water intake can strengthen the organism and assist thwarting degenerative diseases.
All of this may seem hopelessly contradictory. On the one hand, calorie restriction promotes beneficial biological changes that tend to extend life; on the other, there are built in mechanisms that when triggered by chronic calorie restriction can trigger other health problems. These are complex issues, and any extreme measure is likely to cause more problems than it solves.
César Chávez undertook a number of spiritual fasts, including a 25-day fast in 1968 promoting the principle of nonviolence, and a fast of 'thanksgiving and hope' to prepare for pre-arranged civil disobedience by farm workers. Chávez regarded a spiritual fast as "a personal spiritual transformation". Other progressive campaigns have adopted the tactic.