User:Ddotdalllas/Intermittent fasting

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Intermittent fasting, also known as intermittent energy restriction, is an umbrella term for various meal timing schedules that cycle between voluntary fasting (or reduced calorie intake) and non-fasting over a given period. Methods of intermittent fasting include alternate-day fasting, periodic fasting, and daily time-restricted feeding.

Intermittent fasting may have similar effects to a calorie-restriction diet, and has been studied in the 21st century as a practice to possibly reduce the risk of diet-related diseases, such as metabolic syndrome. A 2019 review concluded that intermittent fasting may help with obesity, insulin resistance, dyslipidemia, hypertension, and inflammation.

Intermittent fasting has been criticized as a fad. The science concerning intermittent fasting is contested. The American Heart Association stated in 2017 that intermittent fasting may produce weight loss, reduce insulin resistance, and lower the risk of cardiometabolic diseases, although its long-term sustainability is unknown. The US National Institute on Aging stated in 2018 that there is insufficient evidence to recommend intermittent fasting, and encourages speaking to one's healthcare provider about the benefits and risks before making any significant changes to one's eating pattern.

Fasting exists in various religious practices, including Buddhism, Christianity, Hinduism, Islam, Jainism, and Judaism.

Types
Three methods of intermittent fasting are alternate-day fasting, periodic fasting, and time-restricted feeding:


 * Alternate-day fasting involves alternating between a 24-hour "fast day" when the person eats less than 25% of usual energy needs, followed by a 24-hour non-fasting "feast day" period. It is the strictest form of intermittent fasting because there are more days of fasting per week. There are two subtypes:
 * Complete alternate-day fasting (or total intermittent energy restriction), where no calories are consumed on fast days.
 * Modified alternate-day fasting (or partial intermittent energy restriction) which allows the consumption of up to 25% of daily calorie needs on fasting days instead of complete fasting. This is akin to alternating days with normal eating and days with a very-low-calorie diet.
 * Periodic fasting or whole-day fasting involves any period of consecutive fasting of more than 24 hours, such as the 5:2 diet where there are one or two fast days per week, to the more extreme version with several days or weeks of fasting. A type of periodic fasting known as the 5:2 diet was popularized in the UK and Australia by Michael Mosley around 2012.  During the fasting days, consumption of approximately 500 to 700 calories, or about 25% of regular daily caloric intake, may be allowed instead of complete fasting.
 * Time-restricted feeding involves eating only during a certain number of hours each day. Skipping a meal, the 16:8 diet (16 fasting hours cycled by 8 non-fasting hours), and the 20:4 diet (20 hours fasting with a 4 hour feeding window) are examples. This schedule is thought to leverage the circadian rhythm.

The science concerning intermittent fasting is preliminary and uncertain due to an absence of studies on its long term effects. Preliminary evidence indicates that intermittent fasting may be effective for weight loss, may decrease insulin resistance and fasting insulin, and may improve cardiovascular and metabolic health, although the long term sustainability of these effects has not been studied.

Body weight
There is limited evidence that intermittent fasting produces weight loss comparable to a calorie restricted diet. Most studies on intermittent fasting in humans have observed weight loss, ranging from 2.5% to 9.9%.

The reductions in body weight can be attributed to the loss of fat mass and some lean mass. For time restricted eating the ratio of weight loss is 3:1 for fat mass to lean mass, respectively. Alternate-day fasting does not affect lean body mass, although one review found a small decrease.

Alternate-day fasting improves cardiovascular and metabolic biomarkers similarly to a calorie restriction diet in people who are overweight, obese or have a metabolic syndrome. As of 2021, it remains uncertain whether intermittent fasting could prevent cardiovascular disease.

A 2018 study of 88 obese women over 10 weeks showed that those who used both calorie-restriction and intermittent fasting were more successful at losing weight than the group who used only calorie restriction, or only intermittent fasting. A 2020 study of time-restricted eating over a three-month period in obese people, using a sample of 116 participants, showed there were no effects on body weight or metabolic biomarkers, with experts indicating that the study was too short in duration to show an effect on weight loss. A 2021 review found that intermittent fasting may help people lose more weight than regular eating patterns, but was not different than energy restriction diets.

Intermittent fasting has not yet been studied in children, elderly, or underweight people, and may be harmful in these populations. Intermittent fasting is not recommended for people who are not overweight, and the long-term sustainability of intermittent fasting is unknown.

Other effects
Night-time eating is linked to impaired sleep quality. Intermittent fasting is not recommended to treat cancer in France, the United Kingdom, or the United States, although a few small-scale clinical studies suggest that it may reduce chemotherapy side effects. Periodic fasting may have a minor effect on chronic pain and mood disorders. In preliminary research, intermittent fasting has shown signs of reducing risk factors for certain disorders, including insulin resistance and cardiovascular disease. Intermittent fasting does not affect bone health.

Adverse effects
Reviews of preliminary clinical studies found that short-term intermittent fasting may produce minor adverse effects, such as continuous feelings of hunger, irritability, dizziness, nausea, headaches, and impaired thinking, although these effects disappear within a month from the fasting practice. However, the data remains sparse, as most of the studies did not analyze adverse effects specifically. A 2018 systematic review found no major adverse effects. Intermittent fasting is not recommended for pregnant or breastfeeding women, growing children and adolescents, the elderly, or individuals with, or vulnerable to, eating disorders.

Religious fasting
Intermittent fasting exists in some religious practices. These include the Black Fast of Christianity (commonly practiced during Lent), Vrata (Hinduism), Ramadan (Islam), Fast Sunday (The Church of Jesus Christ of Latter-day Saints), Jain fasting, and Buddhist fasting. Religious fasting practices may only require abstinence from certain foods or last for a short period of time and cause negligible effects.

In Christianity, many adherents of Christian denominations including Catholics, Lutherans, Methodists, Anglicans, and the Orthodox, often observe the Friday Fast throughout the year, which commonly includes abstinence from meat. Throughout the liturgical season of Lent (and especially on Ash Wednesday and Good Friday) in the Christian calendar, many Christians practice a form of intermittent fasting in which one can consume two collations and one full meal; others partake of the Black Fast, in which no food is consumed until sundown.

In Buddhism, fasting is undertaken as part of the monastic training of Theravada Buddhist monks, who fast daily from noon to sunrise of the next day. This daily fasting pattern may be undertaken by laypeople following the eight precepts.

During Ramadan, Islamic practices are similar to intermittent fasting by not eating or drinking from dawn until sunset, while permitting food intake in the morning before dawn and in the evening after dusk for 30 days. A meta-analysis on the health of Muslims during Ramadan shows significant weight loss during the fasting period of up to 1.51 kg, but this weight was regained within about two weeks thereafter. The analysis concluded that "Ramadan provides an opportunity to lose weight, but structured and consistent lifestyle modifications are necessary to achieve lasting weight loss." One review found similarities between Ramadan and time-restricted feeding, with the main dissimilarity being the disallowance of water drinking with Islamic fasting. Ramadan fasting was found to cause a significant decrease in LDL cholesterol levels, and a slight decline in overall cholesterol.

A review of the metabolic effects of fasting showed that religious fasting proved to be beneficial in terms of "body weight and glycemia, cardiometabolic risk markers, and oxidative stress parameters", where animals, in the study, that followed a diet regimen consistent with that of religious fasting, were observed to have weight loss in addition to "lowered plasma levels of glucose, triacylglycerol, and insulin growth factor-1". Negative effects of Ramadan fasting include increased risk of hypoglycemia in diabetics, as well as inadequate levels of certain nutrients. Ramadan disallows fluids during the fasting period. This type of fasting would be hazardous for pregnant women, as it is associated with risks of inducing labor and causing gestational diabetes, although it does not appear to affect the child's weight. For these reasons, pregnant women, as well as children who have not reached puberty, the elderly, those who are physically or mentally incapable of fasting, travelers, and breast-feeding mothers are often exempt from religious fasting — Ramadan being one example.