This type of dietary pattern would be difficult for someone who eats every few hours (e.g., snacks between meals, grazes). It would also not be appropriate for those with conditions that require food at regular intervals due to metabolic changes caused by their medications, such as with diabetes. Prolonged periods of food deprivation or semi-starvation places one at risk for overeating when food is reintroduced, and may foster unhealthy behaviors such as an increased fixation on food. [7,8]
In a randomized trial of 107 overweight or obese premenopausal women, researchers found that participants who followed an intermittent food energy restriction plan (25 percent restriction two days a week) lost a comparable amount of weight to the participants who followed a continuous energy restriction plan. After six months, participants following the intermittent calorie restriction plan lost an average of 14 pounds each. Results were published in 2011 in the International Journal of Obesity.
Also, for many people, a full 16 hours of fasting just isn’t realistic, says Cynthia Sass, a New York City– and L.A.-based performance nutritionist. She recommends 12 hours of overnight fasting at most and believes the 16-hour gap is especially tough on those who exercise early in the morning or late at night. “If fasting makes you feel miserable and results in intense cravings and rebound overeating, it's not the right path for you,” she says.
Dr. Michael Mosley popularized this variation of intermittent fasting in his book ‘The Fast Diet’. This involves 5 regular eating days and 2 fasting days. However, on these two fasting days, it is permitted to eat 500 calories on each day. These calories can be consumed at any time during the day – either spread throughout the day, or as a single meal.
Prolonged very low calorie diets can cause physiological changes that may cause the body to adapt to the calorie restriction and therefore prevent further weight loss.  Intermittent fasting attempts to address this problem by cycling between a low calorie level for a brief time followed by normal eating, which may prevent these adaptations. However, research does not consistently show that intermittent fasting is superior to continuous low calorie diets for weight loss efficiency.
Longo warned that any fasting diet should start with a visit to the doctor. Fasting studies have not been done in children, very elderly people, or people who are underweight — so it’s possible fasting could be harmful in these cases. “If you’re a diabetic and taking insulin or any other drugs, or if you have metabolic disorders, you should not fast,” he added, noting that fasts done poorly can also increase the risk of gallstones.
Hi I'm happy that I was able to accomplish this 1st week...but I would honestly say that I feel tired and want to sleep.....I prayed and try to stay connected with my heavenly father, but honestly it is really hard when you are fasting alone and you still need to continue with a regular schedule...such as cooking for your children....go to work....and attend different activities that are required. Please pray for me so I can continue this fast but on another level, I need strength, motivation and continue with the main goal that is a closer and meaningful relationship with Him. :(
Still, researchers are exploring whether fasting might help fight cancer, or help cancer patients tolerate chemotherapy. And they’re putting serious thought into whether fasting has a role in treating and preventing diabetes, cardiovascular disease, and multiple sclerosis. But while the animal literature is rich, the literature in humans is promising — though far from conclusive. As this 2017 review of the science found, the studies on fasting to control Type 2 diabetes come to contradictory results, and there’s “minimal data” comparing the effects of fasting to plain old calorie restriction in overweight or obese people with the disease. There were also no studies on fasting and human cancer rates.
While this verse applies to our eternal destiny, the principle applies to our daily sojourn; as we humble and deprive our bodies through fasting, our spiritual man is made stronger and our senses more acute. This principle served the apostles well during the early church days. Their decisions were made through fasting and prayer; God gave them instructions and directions. “While they were worshiping the Lord and fasting, the Holy Spirit said, ‘Set apart for me Barnabas and Saul for the work to which I have called them.’ So after they had fasted and prayed, they placed their hands on them and sent them off” (Acts 13:2-3).
The Bible has a great deal to say about both fasting and praying, including commands to fast and pray. The Bible also gives us examples of people who fasted and prayed, using different types of fasts for different reasons, all of which are very positive results. Jesus fasted and prayed. Jesus' disciples fasted and prayed after the Resurrection. Many of the Old Testament heroes and heroines of the faith fasted and prayed. The followers of John the Baptist fasted and prayed.Many people in the early church fasted and prayed. What the Scriptures have taught us directly and by the examples of the saints is surely something we are to do.
For members of The Church of Jesus Christ of Latter-day Saints, fasting is total abstinence from food and drink accompanied by prayer. Members are encouraged to fast on the first Sunday of each month, designated as Fast Sunday. During Fast Sunday, members fast for two consecutive meals (24 hours); this is usually Sunday breakfast and lunch, thus the fasting occurs between the evening meal on Saturday and the evening meal on Sunday. The money saved by not having to purchase and prepare meals is donated to the church as a fast offering, which is then used to help people in need. Members are encouraged to donate more than just the minimal amount, and be as generous as possible. The late LDS President Gordon B. Hinckley asked: "Think ... of what would happen if the principles of fast day and the fast offering were observed throughout the world. The hungry would be fed, the naked clothed, the homeless sheltered. … A new measure of concern and unselfishness would grow in the hearts of people everywhere." Fasting and the associated donations for use in assisting those in need, are an important principle as evidenced by Church leaders addresses on the subject during General Conferences of the Church, e.g. The blessing of a proper fast in 2004, Is Not This the Fast That I Have Chosen? in 2015
Saint Augustine's Prayer Book defines "Fasting, usually meaning not more than a light breakfast, one full meal, and one half meal, on the forty days of Lent." Abstinence, according to Saint Augustine's Prayer Book, "means to refrain from some particular type of food or drink. One traditional expression of abstinence is to avoid meat on Fridays in Lent or through the entire year, except in the seasons of Christmas and Easter. It is common to undertake some particular act of abstinence during the entire season of Lent. This self-discipline may be helpful at other times, as an act of solidarity with those who are in need or as a bodily expression of prayer."