Among the Western religions, only Zoroastrianism prohibits fasting, because of its belief that such a form of asceticism will not aid in strengthening the faithful in their struggle against evil. The other Western religions—Judaism, Christianity, and Islam—emphasize fasting during certain periods. Judaism, which developed many dietary laws and customs, observes several annual fast days, primarily on days of penitence (such as Yom Kippur, the Day of Atonement) or mourning. Christianity, especially Roman Catholicism and Eastern Orthodoxy, has observed a 40-day fast period during Lent, a spring period of penitence before Easter, and during Advent, a penitential period before Christmas. Among Roman Catholics the observance has been modified since the Second Vatican Council (1962–65) to allow greater individual choice, with mandatory fasting only on Ash Wednesday and Good Friday during Lent. Protestant churches generally leave the decision to fast to individual church members. The month of Ramadan in Islam is a period of penitence and total fasting from dawn to dusk.
Embrace a healthy body image. Reject the dualistic way of thinking about people’s bodies that’s so popular in our culture. Your body and spirit aren’t two separate entities; they’re united as one whole. When you understand the profound connections between your body and spirit, it will become natural for you to respond to spiritual experiences by doing something physical like fasting.
In Northern Ireland in 1981, a prisoner, Bobby Sands, was part of the 1981 Irish hunger strike, protesting for better rights in prison. Sands had just been elected to the British Parliament and died after 66 days of not eating. His funeral was attended by 100,000 people and the strike ended only after nine other men died. In all, ten men survived without food for 46 to 73 days.
Remember, fasting is for one’s spiritual health, which involves abstaining from food and drink while spending a lot of extra time in prayer and Bible study (Exodus 34:28 Exodus 34:28And he was there with the LORD forty days and forty nights; he did neither eat bread, nor drink water. And he wrote on the tables the words of the covenant, the ten commandments.
Every person I know needs a breakthrough in some area of his or her life. I am no exception. I need breakthroughs all the time -- it may be a breakthrough in understanding a situation, a breakthrough answer to a problem, a breakthrough idea, a breakthrough insight, a breakthrough in financial or material provision, a breakthrough in health. If you have any need in your life, you need a breakthrough from God to meet that need! Fasting and prayer break the yoke of bondage and bring about a release of God's presence, power, and provision.
Physiologically, calorie restriction has been shown in animals to increase lifespan and improve tolerance to various metabolic stresses in the body.  Although the evidence for caloric restriction in animal studies is strong, there is less convincing evidence in human studies. Proponents of the diet believe that the stress of intermittent fasting causes an immune response that repairs cells and produces positive metabolic changes (reduction in triglycerides, LDL cholesterol, blood pressure, weight, fat mass, blood glucose). [3,5] An understandable concern of this diet is that followers will overeat on non-fasting days to compensate for calories lost during fasting. However, studies have not shown this to be true when compared with other weight loss methods. 
^ Harris, Elizabeth J. (7 June 2010). "Violence and Disruption in Society: A Study of the Early Buddhist Texts". Access to Insight. John T. Bullitt. Retrieved 7 June 2011. If you, Rahula, are desirous of doing a deed with the body, you should reflect on the deed with the body, thus: "That deed which I am desirous of doing with the body is a deed of the body that might conduce to the harm of self and that might conduce to the harm of others and that might conduce to the harm of both; this deed of body is unskilled (akusala), its yield is anguish, its result is anguish.
When a feast day occurs on a fast day, the fast is often mitigated (lessened) to some degree (though meat and dairy are never consumed on any fast day). For example, the Feast of the Annunciation almost always occurs within the Great Lent in the Orthodox calendar: in this case fish (traditionally haddock fried in olive oil) is the main meal of the day.
What makes fasting seem so novel is that, with all the diet advice out there, the easiest might be to simply not eat. Of course, fasting isn’t the same as starving yourself, which is what many people think when they hear “fasting.” And yet, fasting isn’t a diet, either. The literal definition of fasting is to abstain from food and drink from a specific period of time; it’s been around for thousands of years, as spiritual fasting is a part of many religions. But in this context, I prefer looking at fasting as simply a change in eating patterns.
That breakthrough might be in the realm of the spirit. It may be in the realm of your emotions or personal habits. It may be in the realm of a very practical area of life, such as a relationship or finances. What I have seen repeatedly through the years-not only in the Scriptures but in countless personal stories that others have told me -- is that periods of fasting and prayer produce great spiritual results, many of which fall into the realm of a breakthrough. What wasn't a reality . . . suddenly was. What hadn't worked . . . suddenly did. The unwanted situation or object that was there . . . suddenly wasn't there. The relationship that was unloving . . . suddenly was loving. The job that hadn't materialized . . . suddenly did.
I have had my best workouts completely fasted! Once you adapt to training in the fasted state you get a boost of energy and strength. I think this goes back to stimulating the sympathetic system (fight or flight). In addition Fasted training has been shown to increase insulin sensitivity and improve nutrient partitioning. This means that your body will be more efficient at directing nutrients into muscle cells and away from fat stores. Thus training in the fasted state makes the subsequent meals more anabolic. This is why I absolutely love intermittent fasting for fat loss and building muscle. With that said pre- workout protein is beneficial at increasing protein synthesis, elevating metabolism and reducing muscle breakdown. Therefore I recommend 10 grams of BCAA before an intermittent fasting workout.
The purpose of fasting is never explicitly stated in Scripture but its connection to penitence, mourning, and supplication suggests a self-denial that opens one to God and to the immaterial aspects of life. Inasmuch as food and drink typify life in the flesh and all its demands and satisfactions, their absence or rejection speaks to the reality of a higher dimension, one in which the things of the spirit predominate. The theology of fasting, then, is a theology of priorities in which believers are given the opportunity to express themselves in an undivided and intensive devotion to the Lord and to the concerns of the spiritual life.
A recent study completed by the German Cancer Research Center concluded that intermittent fasting indeed “helps lose weight and promotes health,” and noted that the regimen proved especially adept at getting rid of fat in the liver. A USC study also found that the diet reduced participants’ risk of cancer, diabetes, heart disease, and other age-related diseases. While researchers involved cautioned that more testing is necessary, the results are at least encouraging.
Harvie believes fasting might be here to stay, partly because it’s flexible. People can choose a fasting practice and nutrient plan that fits their lifestyle, she says. “We twitter on about which diets are better. But at the end of the day, a diet is only as good as the person who follows it,” says Harvie. “For some people, the 5:2 will be perfect, and for others, it will be absolutely awful.”
The trial, which aimed to investigate how food deprivation affects the aging process, involved 218 normal and slightly overweight men and women between the ages of 21 and 51. Of the group, 143 of them were tasked with following CR, eating 25 percent fewer calories than usual — a decrease deemed feasible based on animal studies. They were to keep this regimen for two years with help from a behavioral intervention team and dietitians to make sure they were getting basic nutrition.
Save high-intensity interval training and heavy weight training for feed days/during your feed window, if you can, when you have the calories for fuel and nutrients for recovery. But if your training schedule calls for a grueling workout on a fast day that can’t be moved, add the calories burned to your count for the day so you don’t burn through muscle. At 200 or 300 calories, you don’t need to compensate, but if you burn 500 or more on a fast day, instead of just 500 maintenance calories with 50g of protein, eat 1,000 calories with 80g or more of protein, Varady advises.
Intermittent fasting is the hottest dieting trend since keto. (Bonus points if you’re keto and intermittently fasting. You can probably fly now!) The gist is that people attempt to lose weight by only eating between certain hours, or they restrict their eating on certain days of the week while allowing themselves to eat normally the rest of the time. That’s the “intermittent” part: Eat regularly most of the time, restrict your eating other times. Then there’s a subset of intermittent fasting known as the 5:2 diet, in which people eat regularly five days of the week and take in a very restricted number of calories on two days.
I am on my 5th week on 16/8.i have lost significantly amount of weight.i just love it,feel lighter.usually eat proteins ,vegetables ,fruits sometimes a little carbs..i break my fast and eat through out till 8pm.between 8pm and 12pm ,i constantly drink water and green tea which makes me feel good when i am on ketosis.i think 16/8 and keto is almost one thing.they just work the same,but what i have noticed is that 16/8 combined with keto diet works perfectly well.good like guys,this is the way to go especially for us ladies!!!
Boosts metabolism: Intermittent fasting also boosts protein, fat, and glucose metabolism in animal studies. Boosting your resting metabolism helps your body burn more calories throughout the day, even while you rest. Fasting also increases your levels of adrenaline and noradrenaline, hormones that help your body free up more stored energy (that’s your body fat) during a fast.
Intermittent fasting (specifically the 5:2 diet) became popular in the UK in 2012 after the BBC2 television Horizon documentary Eat, Fast and Live Longer. Via sales of best-selling books, it became widely practiced. In the United States, intermittent fasting has become a trend among Silicon Valley companies. According to NHS Choices as of 2012, people considering the 5:2 diet should first consult a physician, as fasting can sometimes be unsafe. A news item in the Canadian Medical Association Journal expressed concern that promotional material for the diet showed people eating high-calorie food, such as hamburgers and chips, and that this could encourage binge eating since the implication was that "if you fast two days a week, you can devour as much junk as your gullet can swallow during the remaining five days".
Fasting or intermittent calorie restriction may affect cancer and tumor development, but are not currently used as a form of treating cancer. In 2011, the American Cancer Society recommended that people undergoing chemotherapy increase their intake of protein and calories, but provided evidence that a short-term period of fasting may have benefits during chemotherapy. Chronic fasting is not recommended for people with cancer at risk for weight loss or a suppressed immune system.