As fasting has grown in popularity, scientists and nutritionists have developed different methods of the practice. Some, such as Allen, practice time-restricted feeding, like the 20:4 regimen. Some push the approach to 23:1, cramming all their eating into one hour of a 24-hour day. Other approaches space out fasting days throughout the week, such as the 5:2 method — two days of fasting over seven days. Some enthusiasts supplement their practice with dayslong fasts.
As far back as the 1930s, scientists have been exploring the benefits of reducing calories by skipping meals. During that time, one American scientist found that significantly reducing calories helped mice live longer, healthier lives. More recently, researches have found the same in fruit flies, roundworms and monkeys. Studies have also shown that decreasing calorie consumption by 30 to 40 percent (regardless of how it’s done) can extend life span by a third or more. Plus, there’s data to suggest that limiting food intake may reduce the risk of many common diseases. Some believe fasting may also increase the body’s responsiveness to insulin, which regulates blood sugar and helps control hunger.
Cons: Even though it’s nice to eat a few snacks rather than go without any food for 20-plus hours, the guidelines for what you need to eat (and when) can be hard to follow long-term. The strict schedule and meal plan may also interfere with social gatherings. Additionally, eating one main meal at night — while following strict guidelines of what to eat, and in what order — can be tough. It’s especially hard for those who prefer not to eat large meals late in the day.

The ancient Greek physician Hippocrates wrote, “To eat when you are sick, is to feed your illness”. Another ancient Greek writer and historian Plutarch is also credited with penning “Instead of using medicine, better fast today”. In more recent times one of our founding fathers, Benjamin Franklin, stated, “The best of all medicines is resting and fasting”.
There may also be other intermittent fasting benefits: A 2017 study from the University of Southern California followed 71 adults who were placed on a low-calorie, fasting-mimicking diet for five days each month for three months. After following the diet, researchers found that the diet reduced cardiovascular risks, including blood pressure, inflammation, and body fat, in participants. A 2018 study from the British Journal of Nutrition backs this up after overweight participants followed the 5:2 method and saw improvements in their triglyceride levels and blood pressure. Other studies have also shown that IF may help with relieving MS symptoms, but more studies are needed on a larger scale and for a longer period of time to support these claims.
Thank you very much for the great article. As a Muslim, we are encouraged to fast two days a week (Monday and Thursday)! It is not a must, just preferred. We fast from sunrise to sunset. No food or drink is allowed during this period (no water). As you mentioned a true fast can be a mental and physical cleansing time. From a personal experience, fasting is really great. I strongly believe it has many benefits on the mind and body as well if done correctly.
Spending time in prayer and fasting is not automatically effective in accomplishing the desires of those who fast. Fasting or no fasting, God only promises to answer our prayers when we ask according to His will. 1 John 5:14-15 tells us, "This is the confidence we have in approaching God: that if we ask anything according to his will, he hears us. And if we know that he hears us - whatever we ask - we know that we have what we asked of him." In the prophet Isaiah's time, the people grumbled that they had fasted, yet God did not answer in the way they wanted (Isaiah 58:3-4). Isaiah responded by proclaiming that the external show of fasting and prayer, without the proper heart attitude, was futile (Isaiah 58:5-9).

Many healers claim that fasting is a particularly useful therapy for Americans and for the modern lifestyle, subjected to heavy diets, overeating, and constant exposure to food additives and chemicals. Some alternative practitioners have gone so far as to estimate that the average American is carrying 5-10 pounds of toxic substances in their bodies, for which fasting is the quickest and most effective means of removal.
In addition to our attitudes towards God and our stance before man, our motives must also be correct. We should fast in order to further the building up of God’s kingdom by seeking to minister to others. The prophet Isaiah received from the Lord the acceptable motives for our fasts: “Is not this the kind of fasting I have chosen: to loose the chains of injustice and untie the cords of the yoke, to set the oppressed free and break every yoke? Is it not to share your food with the hungry and to provide the poor wanderer with shelter -- when you see the naked, to clothe him, and not to turn away from your own flesh and blood?” (Isaiah 58:6-7).
I have found that the 4:3 style fasts have worked well for my friends and me based on our work/life schedule and our personal health goals. I like that full day fasts feel like an on/off switch — I don’t think about eating on fast days and on eat days if I happen to overeat, I don’t feel guilty about it (since I’m eating at a deficit during the week). I find it more manageable to cut calories over a week (using the 4:3 style of IF) instead of every day (trying to eating less daily).
In the religions of some tribes of Native Americans, fasting was practiced before and during a vision quest. Among the Evenk of Siberia, shamans (religious personages thought to have the power to heal and to communicate psychically) often received their initial visions not with a quest but rather after an unexplained illness. After the initial vision, however, they fasted and trained themselves to see further visions and to control spirits. Historically, priestly societies among the Pueblo Indians of the American Southwest fasted during retreats before major ceremonies connected with seasonal changes.
About that: People don’t usually binge that much on their feed day. “Most people report they can only eat about 10% more coming off a fast than they normally would—their body just won’t let them overeat,” Varady says. That’s why an increasing number of studies show that intermittent fasting may work just as well as limiting your calorie intake when it comes to weight loss.
In addition to these, there is the fast of repentance which a person keeps after committing sin, it being imposed as a penance by the priest for seven days, forty days or one year. There is also a fast which a bishop keeps at the time he is consecrated. Also there are fasts that are widely observed but which have not been included in the canon of the church and which are therefore considered strictly optional such as the "Tsige Tsom" or Spring Fast, also known as "Kweskwam Tsom" which marks the exile of the Holy Family in Egypt.
In addition to the fasts mentioned above, Roman Catholics must also observe the Eucharistic Fast, which involves taking nothing but water and medicines into the body for one hour before receiving the Eucharist. The ancient practice was to fast from midnight until Mass that day, but as Masses after noon and in the evening became common, this was soon modified to fasting for three hours. Current law requires merely one hour of eucharistic fast, although some Roman Catholics still abide by the older rules.
In practice, however, I would be concerned with eating enough. Based on my experience, teaching yourself to consistently eat more is one of the harder parts of intermittent fasting. You might be able to feast for a meal, but learning to do so every day of the week takes a little bit of planning, a lot of cooking, and consistent eating. The end result is that most people who try intermittent fasting end up losing some weight because the size of their meals remains similar even though a few meals are being cut out each week.
The second one is more subtle: The body shifts into fat-burning mode when it doesn’t get food for an extended period of time. That’s because the body’s first source of fuel is glycogen, and it only turns to burning body fat once that quickly available energy source is depleted. So when you fast for long enough, you drive down stores of glycogen and start burning fat tissue. “In people, we see a change in fasting glucose — it’s lower — and abdominal fat is affected without much of an effect on the muscles,” Longo explained.
An informative description of the proclamation of a fast is in Jeremiah 36:9. There the people of Judah convened, apparently for the purpose of national repentance. This at least is what Jeremiah instructed Baruch to encourage them to do (vv. 7-8). Moreover, Jeremiah refers to the anticipated event as a "day of fasting" (v. 6), suggesting a common practice known to him and the people generally. In fact, Isaiah had spoken of such convocations a century earlier ( 58:3-6 ), gatherings on special days for special purposes. Regardless of Isaiah's feelings about the abuse of fasting, it is obvious that he recognized it as a legitimate form of worship and that he found no fault with it being carried out on specially called occasions.
American King James Version×), though other national fast days are mentioned in the Bible. Also, personal fasts are clearly expected of Christ’s disciples (Matthew 9:14-15 Matthew 9:14-15 14 Then came to him the disciples of John, saying, Why do we and the Pharisees fast oft, but your disciples fast not? 15 And Jesus said to them, Can the children of the bridal chamber mourn, as long as the bridegroom is with them? but the days will come, when the bridegroom shall be taken from them, and then shall they fast.

You’re consuming less food and thus spending less money. Rather than overeating to put on 1 pound of muscle and 4 pounds of fat in a week or two, you’re aiming to eat exactly enough to put on 1 pound of muscle without adding much fat on top of it.  Yeah, it’s a delicate balance, but there’s far less swing involved. You are just slowly, steadily, and consistently building muscle and strength over many months.
The problem is that too many people jump on the fasting bandwagon without understanding how to assess its impact. Once a plan has been integrated into your everyday life, you should take time every week or month to analyze how things are going. Even if weight loss is your primary goal, it’s important to consider how fasting is affecting other aspects of your health, such as your energy levels, ability to exercise and digestion. Here are some questions you should ask yourself.

This handy reference guide, Seven Basic Steps to Successful Fasting and Prayer, will help make your time with the Lord more spiritually rewarding. I encourage you to keep it with you during your fast and refer to it often because it gives easy-to-follow suggestions on how to begin your fast, what to do while you fast, and how to end your fast properly.
Fasting for Jews means completely abstaining from food and drink, including water. Traditionally observant Jews fast six days of the year. With the exception of Yom Kippur, fasting is never permitted on Shabbat, for the commandment of keeping Shabbat is biblically ordained and overrides the later rabbinically instituted fast days. (The optional minor fast of the Tenth of Tevet could also override the Shabbat, but the current calendar system prevents this from ever occurring.[89])
In a physiological context, fasting may refer to the metabolic status of a person who has not eaten overnight, or to the metabolic state achieved after complete digestion and absorption of a meal. Several metabolic adjustments occur during fasting. Some diagnostic tests are used to determine a fasting state. For example, a person is assumed to be fasting once 8–12 hours have elapsed since the last meal. Metabolic changes of the fasting state begin after absorption of a meal (typically 3–5 hours after eating).
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