Intermittent Fasting
   HOME

TheInfoList



OR:

Intermittent fasting is any of various meal timing schedules that cycle between voluntary
fasting Fasting is the abstention from eating and sometimes drinking. From a purely physiological context, "fasting" may refer to the metabolic status of a person who has not eaten overnight (see " Breakfast"), or to the metabolic state achieved after ...
(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 has been studied to find whether it can reduce the risk of diet-related diseases, such as
metabolic syndrome Metabolic syndrome is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL). Metabolic syndrome ...
. A 2019 review concluded that intermittent fasting may help with
obesity Obesity is a medical condition, sometimes considered a disease, in which excess body fat has accumulated to such an extent that it may negatively affect health. People are classified as obese when their body mass index (BMI)—a person's we ...
,
insulin resistance Insulin resistance (IR) is a pathological condition in which cell (biology), cells fail to respond normally to the hormone insulin. Insulin is a hormone that facilitates the transport of glucose from blood into cells, thereby reducing blood gluco ...
,
dyslipidemia Dyslipidemia is an abnormal amount of lipids (e.g. triglycerides, cholesterol and/or fat phospholipids) in the blood. Dyslipidemia is a risk factor for the development of atherosclerotic cardiovascular disease ( ASCVD). ASCVD includes coronary ar ...
,
hypertension Hypertension (HTN or HT), also known as high blood pressure (HBP), is a long-term medical condition in which the blood pressure in the arteries is persistently elevated. High blood pressure usually does not cause symptoms. Long-term high bl ...
, and
inflammation Inflammation (from la, wikt:en:inflammatio#Latin, inflammatio) is part of the complex biological response of body tissues to harmful stimuli, such as pathogens, damaged cells, or Irritation, irritants, and is a protective response involving im ...
. A 2022 review indicated that intermittent fasting is generally safe. Adverse effects of intermittent fasting have not been comprehensively studied, leading some academics to point out its risk as a dietary fad. The US
National Institute on Aging The National Institute on Aging (NIA) is a division of the U.S. National Institutes of Health (NIH), located in Bethesda, Maryland. The NIA itself is headquartered in Baltimore, Maryland. The NIA leads a broad scientific effort to understand the ...
states 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
Islam Islam (; ar, ۘالِإسلَام, , ) is an Abrahamic religions, Abrahamic Monotheism#Islam, monotheistic religion centred primarily around the Quran, a religious text considered by Muslims to be the direct word of God in Islam, God (or ...
,
Christianity Christianity is an Abrahamic monotheistic religion based on the life and teachings of Jesus of Nazareth. It is the world's largest and most widespread religion with roughly 2.38 billion followers representing one-third of the global pop ...
,
Hinduism Hinduism () is an Indian religion or '' dharma'', a religious and universal order or way of life by which followers abide. As a religion, it is the world's third-largest, with over 1.2–1.35 billion followers, or 15–16% of the global p ...
,
Buddhism Buddhism ( , ), also known as Buddha Dharma and Dharmavinaya (), is an Indian religion or philosophical tradition based on teachings attributed to the Buddha. It originated in northern India as a -movement in the 5th century BCE, and gra ...
,
Jainism Jainism ( ), also known as Jain Dharma, is an Indian religions, Indian religion. Jainism traces its spiritual ideas and history through the succession of twenty-four tirthankaras (supreme preachers of ''Dharma''), with the first in the current ...
and
Judaism Judaism ( he, ''Yahăḏūṯ'') is an Abrahamic, monotheistic, and ethnic religion comprising the collective religious, cultural, and legal tradition and civilization of the Jewish people. It has its roots as an organized religion in the ...
.


History

Fasting is an ancient tradition, having been practiced by many cultures and religions over
centuries A century is a period of 100 years. Centuries are numbered ordinally in English and many other languages. The word ''century'' comes from the Latin ''centum'', meaning ''one hundred''. ''Century'' is sometimes abbreviated as c. A centennial or ...
. Therapeutic intermittent fasts for the treatment of obesity have been investigated since at least 1915, with a renewed interest in the medical community in the 1960s after Bloom and his colleagues published an "enthusiastic report". Intermittent fasts, or "short-term starvation periods", ranged from 1 to 14 days in these early studies. This enthusiasm penetrated lay magazines, which prompted researchers and clinicians to caution about the use of intermittent fasts without medical monitoring. A type of periodic fasting known as the 5:2 diet was introduced by Michelle Harvie and
Mark Mattson Mark may refer to: Currency * Bosnia and Herzegovina convertible mark, the currency of Bosnia and Herzegovina * East German mark, the currency of the German Democratic Republic * Estonian mark, the currency of Estonia between 1918 and 1927 * Fi ...
and popularized in the UK and Australia by Michael Mosley around 2012. It also became common in Australia.


Types

Three methods of intermittent fasting are time-restricted feeding, alternate-day fasting, and periodic fasting: * Time-restricted feeding involves eating only during a certain number of hours each day, often establishing a consistent daily pattern of caloric intake within an 8–12-hour time window. This schedule may align food intake with
circadian rhythm A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., Endogeny (biology), endogeno ...
s. * 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. There are two subtypes: ** Complete alternate-day fasting (or total intermittent energy restriction), where no calories are consumed on fasting 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 A very-low-calorie diet (VLCD), also known as semistarvation diet and crash diet, is a type of diet with very or extremely low daily food energy consumption. Often described as a fad diet, it is defined as a diet of per day or less. Modern medica ...
. * 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 fasting days per week, to the more extreme version with several days or weeks of fasting. 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. 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 Insulin resistance (IR) is a pathological condition in which cell (biology), cells fail to respond normally to the hormone insulin. Insulin is a hormone that facilitates the transport of glucose from blood into cells, thereby reducing blood gluco ...
and fasting insulin, and may improve
cardiovascular The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
and
metabolic Metabolism (, from el, μεταβολή ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cell ...
health, although the long term sustainability of these effects has not been studied.


Research


Body weight and metabolic disease risk

There is limited evidence that intermittent fasting produces
weight loss Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat (adipose tissue), or lean mass (namely bone mineral deposits, muscle, tendon, and other conn ...
comparable to a
calorie restricted diet Calorie restriction (caloric restriction or energy restriction) is a dietary regimen that reduces intake of energy from caloric foods & beverages without incurring malnutrition. "Reduce" can be defined relative to the subject's previous intake be ...
. 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 4:1 for fat mass to lean mass, respectively. Alternate-day fasting does not affect
lean body mass Lean body mass (LBM), sometimes conflated with ''fat-free mass'', is a component of body composition. Fat free mass (FFM) is calculated by subtracting body fat weight from total body weight: total body weight is lean plus fat. In equations: :LBM&n ...
, although one review found a small decrease. Alternate-day fasting improves
cardiovascular The blood circulatory system is a system of organs that includes the heart, blood vessels, and blood which is circulated throughout the entire body of a human or other vertebrate. It includes the cardiovascular system, or vascular system, tha ...
and metabolic
biomarker In biomedical contexts, a biomarker, or biological marker, is a measurable indicator of some biological state or condition. Biomarkers are often measured and evaluated using blood, urine, or soft tissues to examine normal biological processes, ...
s similarly to a
calorie restriction diet Calorie restriction (caloric restriction or energy restriction) is a dietary regimen that reduces intake of energy from caloric foods & beverages without incurring malnutrition. "Reduce" can be defined relative to the subject's previous intake be ...
in people who are
overweight Being overweight or fat is having more body fat than is optimally healthy. Being overweight is especially common where food supplies are plentiful and lifestyles are sedentary. , excess weight reached epidemic proportions globally, with mo ...
, obese or have
metabolic syndrome Metabolic syndrome is a clustering of at least three of the following five medical conditions: abdominal obesity, high blood pressure, high blood sugar, high serum triglycerides, and low serum high-density lipoprotein (HDL). Metabolic syndrome ...
. As of 2021, it remains uncertain whether intermittent fasting could prevent cardiovascular disease. Intermittent fasting has not 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 . A 2021 review found that moderate alternate-day fasting for two to six months was associated with reductions of body weight,
body mass index Body mass index (BMI) is a value derived from the mass (weight) and height of a person. The BMI is defined as the body mass divided by the square of the body height, and is expressed in units of kg/m2, resulting from mass in kilograms and he ...
, and cardiometabolic
risk factor In epidemiology, a risk factor or determinant is a variable associated with an increased risk of disease or infection. Due to a lack of harmonization across disciplines, determinant, in its more widely accepted scientific meaning, is often use ...
s in overweight or obese adults.


Other effects

Intermittent fasting is not recommended to treat
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
in France, the United Kingdom, or the United States, although a few small-scale clinical studies suggest that it may reduce
chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemotherap ...
side effects. Periodic fasting may have a minor effect on
chronic pain Chronic pain is classified as pain that lasts longer than three to six months. In medicine, the distinction between Acute (medicine), acute and Chronic condition, chronic pain is sometimes determined by the amount of time since onset. Two commonly ...
and
mood disorder A mood disorder, also known as an affective disorder, is any of a group of conditions of mental and behavioral disorder where a disturbance in the person's mood is the main underlying feature. The classification is in the ''Diagnostic and Stat ...
s. Athletic performance does not benefit from intermittent fasting. Overnight fasting before exercise increases
lipolysis Lipolysis is the metabolic pathway through which lipid triglycerides are hydrolyzed into a glycerol and free fatty acids. It is used to mobilize stored energy during fasting or exercise, and usually occurs in fat adipocytes. The most important ...
, but reduces performance in prolonged exercise (more than 60 min).


Side effects

Reviews of preliminary clinical studies found that short-term intermittent fasting may produce minor side effects, such as continuous feelings of hunger, irritability, dizziness, nausea, headaches, and impaired thinking, although these effects disappear within a month from beginning the fasting practice. A 2018
systematic review A systematic review is a Literature review, scholarly synthesis of the evidence on a clearly presented topic using critical methods to identify, define and assess research on the topic. A systematic review extracts and interprets data from publ ...
found no major adverse effects. Intermittent fasting is not recommended for
pregnant Pregnancy is the time during which one or more offspring develops (gestation, gestates) inside a woman, woman's uterus (womb). A multiple birth, multiple pregnancy involves more than one offspring, such as with twins. Pregnancy usually occur ...
or breastfeeding women, growing children and adolescents, the elderly, or individuals with or vulnerable to
eating disorder An eating disorder is a mental disorder defined by abnormal eating behaviors that negatively affect a person's physical or mental health. Only one eating disorder can be diagnosed at a given time. Types of eating disorders include binge eating d ...
s.


Tolerance

Tolerance of a diet is a determinant of the potential effectiveness and maintenance of benefits obtained, such as
weight loss Weight loss, in the context of medicine, health, or physical fitness, refers to a reduction of the total body mass, by a mean loss of fluid, body fat (adipose tissue), or lean mass (namely bone mineral deposits, muscle, tendon, and other conn ...
or biomarker improvement. A 2019 review found that drop-out rates varied widely from 2% to 38% for intermittent fasting, and from 0% to 50% for
calorie restriction diet Calorie restriction (caloric restriction or energy restriction) is a dietary regimen that reduces intake of energy from caloric foods & beverages without incurring malnutrition. "Reduce" can be defined relative to the subject's previous intake be ...
.


Possible mechanisms

Preliminary research indicates that fasting may induce a transition through four states: # The fed state or absorptive state during
satiety Satiety ( ) is a state or condition of fullness gratified beyond the point of satisfaction, the opposite of hunger. It is a state which induces meal termination.Hetherington, M.Sensory-specific satiety and its importance in meal termination ''Neuro ...
, when the primary fuel source is
glucose Glucose is a simple sugar with the molecular formula . Glucose is overall the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using ...
and body fat storage is active, lasting for about 4 hours; # The postabsorptive state, lasting for up to 18 hours, when
glucagon Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It raises concentration of glucose and fatty acids in the bloodstream, and is considered to be the main catabolic hormone of the body. It is also used as a Glucagon (medicati ...
is secreted and the body uses liver glucose reserves as a fuel source; # The fasted state, transitioning progressively to other reserves, such as fat, lactic acid, and alanine, as fuel sources, when the liver glucose reserves are depleted, occurring after 12 to 36 hours of continued fast; # The shift from preferential
lipid synthesis Lipid metabolism is the synthesis and degradation of lipids in cells, involving the breakdown or storage of fats for energy and the synthesis of structural and functional lipids, such as those involved in the construction of cell membranes. In anim ...
and fat storage, to the
mobilization Mobilization is the act of assembling and readying military troops and supplies for war. The word ''mobilization'' was first used in a military context in the 1850s to describe the preparation of the Prussian Army. Mobilization theories and ...
of fat (in the form of
free fatty acids In chemistry, particularly in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, f ...
), metabolized into fatty acid-derived ketones to provide energy. Some authors call this transition the "metabolic switch". A 2019 review of weight-change interventions, including alternate day fasting, time-restricted feeding, exercise and overeating, found that body weight homeostasis could not precisely correct "energetic errors" – the loss or gain of calories – in the short-term. Another pathway for effects of meal timing on metabolism lies in the influence of the
circadian rhythm A circadian rhythm (), or circadian cycle, is a natural, internal process that regulates the sleep–wake cycle and repeats roughly every 24 hours. It can refer to any process that originates within an organism (i.e., Endogeny (biology), endogeno ...
over the
endocrine system The endocrine system is a messenger system comprising feedback loops of the hormones released by internal glands of an organism directly into the circulatory system, regulating distant target organs. In vertebrates, the hypothalamus is the neu ...
, especially on
glucose metabolism Carbohydrate metabolism is the whole of the biochemical processes responsible for the metabolic formation, breakdown, and interconversion of carbohydrates in living organisms. Carbohydrates are central to many essential metabolic pathways. Pla ...
and
leptin Leptin (from Ancient Greek, Greek λεπτός ''leptos'', "thin" or "light" or "small") is a hormone predominantly made by adipose cells and enterocytes in the small intestine that helps to regulate Energy homeostasis, energy balance by inhib ...
. Preliminary studies found that eating when melatonin is secreted during darkness and commonly when sleeping at night is associated with increased glucose levels in young healthy adults, and obesity and cardiovascular disorders in less healthy individuals. Reviews on obesity prevention concluded that "meal timing appears as a new potential target in weight control strategies" and suggest that "timing and content of food intake, physical activity, and sleep may be modulated to counteract" circadian and metabolic genetic predispositions to obesity.


Intermittent feeding

Other feeding schemes, such as hypocaloric feeding and intermittent feeding, also called bolus feeding were under study. A 2019 meta-analysis found that intermittent feeding may be more beneficial for premature infants, although better designed studies are required to devise clinical practices. In adults, reviews have not found intermittent feeding to increase glucose variability or gastrointestinal intolerance. A meta-analysis found intermittent feeding had no influence on gastric residual volumes and aspiration, pneumonia, mortality nor morbidity in people with a trauma, but increased the risk of diarrhea.


Food production

Intermittent fasting, or "skip-a-day" feeding, is supposedly the most common feeding strategy for
poultry Poultry () are domesticated birds kept by humans for their eggs, their meat or their feathers. These birds are most typically members of the superorder Galloanserae (fowl), especially the order Galliformes (which includes chickens, quails, a ...
in broiler breeder farms worldwide, as an alternative to adding bulky fibers to the diet to reduce growth. It is perceived as welfare-reducing and thus illegal in several European countries including Sweden. Intermittent fasting in poultry appears to increase food consumption but reduce appetitive behaviors such as foraging.


Religious fasting

Intermittent fasting exists in some religious practices. These include the
Black Fast A Black Fast, also known as a strict fast, is an ancient form of Christian fasting. Those undertaking a Black Fast consume no food during the day (although sometimes water is permitted) and then break the fast after sunset with prayer, as well as ...
of
Christianity Christianity is an Abrahamic monotheistic religion based on the life and teachings of Jesus of Nazareth. It is the world's largest and most widespread religion with roughly 2.38 billion followers representing one-third of the global pop ...
(commonly practiced during
Lent Lent ( la, Quadragesima, 'Fortieth') is a solemn religious observance in the liturgical calendar commemorating the 40 days Jesus spent fasting in the desert and enduring temptation by Satan, according to the Gospels of Matthew, Mark and Luke ...
),
Vrata Vrata is a Sanskrit word that means "vow, resolve, devotion", and refers to pious observances such as fasting and pilgrimage ( Tirtha) found in Indian religions such as Jainism and Hinduism. It is typically accompanied with prayers seeking hea ...
(
Hinduism Hinduism () is an Indian religion or '' dharma'', a religious and universal order or way of life by which followers abide. As a religion, it is the world's third-largest, with over 1.2–1.35 billion followers, or 15–16% of the global p ...
),
Ramadan , type = islam , longtype = Religious , image = Ramadan montage.jpg , caption=From top, left to right: A crescent moon over Sarıçam, Turkey, marking the beginning of the Islamic month of Ramadan. Ramadan Quran reading in Bandar Torkaman, Iran. ...
(
Islam Islam (; ar, ۘالِإسلَام, , ) is an Abrahamic religions, Abrahamic Monotheism#Islam, monotheistic religion centred primarily around the Quran, a religious text considered by Muslims to be the direct word of God in Islam, God (or ...
),
Yom Kippur Yom Kippur (; he, יוֹם כִּפּוּר, , , ) is the holiest day in Judaism and Samaritanism. It occurs annually on the 10th of Tishrei, the first month of the Hebrew calendar. Primarily centered on atonement and repentance, the day's ...
(
Judaism Judaism ( he, ''Yahăḏūṯ'') is an Abrahamic, monotheistic, and ethnic religion comprising the collective religious, cultural, and legal tradition and civilization of the Jewish people. It has its roots as an organized religion in the ...
), Fast Sunday (
The Church of Jesus Christ of Latter-day Saints The Church of Jesus Christ of Latter-day Saints, informally known as the LDS Church or Mormon Church, is a Nontrinitarianism, nontrinitarian Christianity, Christian church that considers itself to be the Restorationism, restoration of the ...
),
Jain Jainism ( ), also known as Jain Dharma, is an Indian religion. Jainism traces its spiritual ideas and history through the succession of twenty-four tirthankaras (supreme preachers of ''Dharma''), with the first in the current time cycle being ...
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.


Hinduism

A ''Vrata'' is observed either as an independent private ritual at a date of one's choice, as part of a particular ceremony such as wedding, or as a part of a major festival such as
Diwali Diwali (), Dewali, Divali, or Deepavali ( IAST: ''dīpāvalī''), also known as the Festival of Lights, related to Jain Diwali, Bandi Chhor Divas, Tihar, Swanti, Sohrai, and Bandna, is a religious celebration in Indian religions. It is ...
(Lakshmi, festival of lights),
Shivaratri Maha Shivaratri ( IAST: Mahāśivarātri) is a Hindu festival celebrated annually in honour of the god Shiva. The name also refers to the night when Shiva performs the heavenly dance called Tandava. In every month of the luni-solar Hindu c ...
(Shiva),
Navratri Navaratri is an annual Hindu festival observed in the honour of the goddess Durga. It spans over nine nights (and ten days), first in the month of Chaitra (March/April of the Gregorian calendar), and again in the month of Sharada. It is ob ...
(Durga or Rama), Kandasashti (Muruga),
Ekadashi Ekadashi () is the eleventh lunar day (''tithi'') of each of the two lunar phases which occur in an Vedic calendar month - the '' Shukla Pakṣa'' (the period of the brightening moon also known as the waxing phase) and the ''Kṛṣṇa Pakṣ ...
(Krishna, Vishnu
avatars Avatar (, ; ), is a concept within Hinduism that in Sanskrit literally means "descent". It signifies the material appearance or incarnation of a powerful deity, goddess or spirit on Earth. The relative verb to "alight, to make one's appearance ...
).


Christianity

In Christianity, many adherents of
Christian denomination A Christian denomination is a distinct religious body within Christianity that comprises all church congregations of the same kind, identifiable by traits such as a name, particular history, organization, leadership, theological doctrine, worsh ...
s 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 Ash Wednesday is a holy day of prayer and fasting in many Western Christian denominations. It is preceded by Shrove Tuesday and falls on the first day of Lent (the six weeks of penitence before Easter). It is observed by Catholics in the Rom ...
and
Good Friday Good Friday is a Christian holiday commemorating the crucifixion of Jesus and his death at Calvary. It is observed during Holy Week as part of the Paschal Triduum. It is also known as Holy Friday, Great Friday, Great and Holy Friday (also Hol ...
) in the
Christian calendar The Gregorian calendar is the calendar used in most parts of the world. It was introduced in October 1582 by Pope Gregory XIII as a modification of, and replacement for, the Julian calendar. The principal change was to space leap years dif ...
, many Christians practice a form of intermittent fasting in which one can consume two
collation Collation is the assembly of written information into a standard order. Many systems of collation are based on numerical order or alphabetical order, or extensions and combinations thereof. Collation is a fundamental element of most office fili ...
s and one full meal; others partake of the Black Fast, in which no food is consumed until sundown.


Buddhism

In Buddhism, fasting is undertaken as part of the monastic training of
Theravada ''Theravāda'' () ( si, ථේරවාදය, my, ထေရဝါဒ, th, เถรวาท, km, ថេរវាទ, lo, ເຖຣະວາດ, pi, , ) is the most commonly accepted name of Buddhism's oldest existing school. The school' ...
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.


Islam

During
Ramadan , type = islam , longtype = Religious , image = Ramadan montage.jpg , caption=From top, left to right: A crescent moon over Sarıçam, Turkey, marking the beginning of the Islamic month of Ramadan. Ramadan Quran reading in Bandar Torkaman, Iran. ...
, 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 A meta-analysis is a statistical analysis that combines the results of multiple scientific studies. Meta-analyses can be performed when there are multiple scientific studies addressing the same question, with each individual study reporting me ...
on the health of Muslims during Ramadan shows significant weight loss during the fasting period of up to , 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. In a 2020 review, Ramadan fasting caused a significant decrease in
LDL cholesterol Low-density lipoprotein (LDL) is one of the five major groups of lipoprotein that transport all fat molecules around the body in extracellular water. These groups, from least dense to most dense, are chylomicrons (aka ULDL by the overall dens ...
levels, and a slight decline in
total cholesterol Cholesterol is any of a class of certain organic molecules called lipids. It is a sterol (or modified steroid), a type of lipid. Cholesterol is biosynthesized by all animal cells and is an essential structural component of animal cell membrane ...
. 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, triacylglycerols, and insulin growth factor-1". Negative effects of Ramadan fasting include increased risk of
hypoglycemia Hypoglycemia, also called low blood sugar, is a fall in blood sugar to levels below normal, typically below 70 mg/dL (3.9 mmol/L). Whipple's triad is used to properly identify hypoglycemic episodes. It is defined as blood glucose belo ...
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 Gestational diabetes is a condition in which a woman without diabetes develops high blood sugar levels during pregnancy. Gestational diabetes generally results in few symptoms; however, it increases the risk of pre-eclampsia, depression, and of ...
, 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.


Recommendations


United States

The
American Heart Association The American Heart Association (AHA) is a nonprofit organization in the United States that funds cardiovascular medical research, educates consumers on healthy living and fosters appropriate cardiac care in an effort to reduce disability and death ...
(AHA) says that as with other fads diets, there is no good evidence of heart health benefits from intermittent fasting. The
American Diabetes Association The American Diabetes Association (ADA) is a United States-based nonprofit that seeks to educate the public about diabetes and to help those affected by it through funding research to manage, cure and prevent diabetes (including type 1 diabetes, ...
"found limited evidence about the safety and/or effects of intermittent fasting on
type 1 diabetes Type 1 diabetes (T1D), formerly known as juvenile diabetes, is an autoimmune disease that originates when cells that make insulin (beta cells) are destroyed by the immune system. Insulin is a hormone required for the cells to use blood sugar for ...
" and preliminary results of weight loss for
type 2 diabetes Type 2 diabetes, formerly known as adult-onset diabetes, is a form of diabetes mellitus that is characterized by high blood sugar, insulin resistance, and relative lack of insulin. Common symptoms include increased thirst, frequent urination, ...
, and so does not recommend any specific dietary pattern for the management of diabetes until more research is done, recommending instead that "health care providers should focus on the key factors that are common among the patterns". The National Institute on Aging states that although intermittent fasting showed weight loss success in several studies on obese or overweight individuals, it does not recommend intermittent fasting for non-overweight individuals because of uncertainties about its effectiveness and safety, especially for older adults.


New Zealand

The New Zealand's Ministry of Health considers that intermittent fasting can be advised by doctors to some people, except diabetics, stating that these "diets can be as effective as other energy-restricted diets, and some people may find them easier to stick to" but there are possible side effects during fasting days such as "hunger, low energy levels, light-headedness and poor mental functioning" and note that healthy food must be chosen on non-fasting days.


United Kingdom

According to
NHS Choices The National Health Service (NHS) is the publicly funded healthcare system in England, and one of the four National Health Service systems in the United Kingdom. It is the second largest single-payer healthcare system in the world after th ...
, 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 The ''Canadian Medical Association Journal'' (French ''Journal de l'Association Médicale Canadienne'') is a peer-reviewed general medical journal published by the Canadian Medical Association (CMA). It publishes original clinical research, anal ...
'' expressed concern that promotional material for the 5:2 diet showed people eating high-calorie food, such as hamburgers and chips, and that this could encourage
binge eating Binge eating is a pattern of disordered eating which consists of episodes of uncontrollable eating. It is a common symptom of eating disorders such as binge eating disorder and bulimia nervosa. During such binges, a person rapidly consumes an ex ...
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". Binge eating following dietary restrictions has been observed in a post-war famine study, where nineteen prisoners of war were observed during their rehabilitation with unlimited access to food, and found they tended to engage in binge eating.


Europe

Given the lack of advantage and the increased incidence of diarrhea, European guidelines do not recommend intermittent feeding for people in intensive care units.


Usage trends

, intermittent fasting was a common
fad diet A fad diet is a diet that becomes popular for a short time, similar to fads in fashion, without being a standard dietary recommendation, and often making unreasonable claims for fast weight loss or health improvements. There is no single defini ...
, attracting celebrity endorsements and public interest.


UK and Australia

Intermittent fasting (specifically the 5:2 diet) was popularized by Michael Mosley in the UK and Australia in 2012 after the
BBC2 BBC Two is a British free-to-air public broadcast television network owned and operated by the BBC. It covers a wide range of subject matter, with a remit "to broadcast programmes of depth and substance" in contrast to the more mainstream an ...
television ''Horizon'' documentary '' Eat, Fast and Live Longer''.


North America

In the United States, intermittent fasting became a fad in
Silicon Valley, California Silicon Valley is a region in Northern California that serves as a global center for high technology and innovation. Located in the southern part of the San Francisco Bay Area, it corresponds roughly to the geographical areas San Mateo Cou ...
. It was the most popular diet in 2018, according to a survey by the
International Food Information Council Founded in 1985, the International Food Information Council (IFIC) is a nonprofit organization supported by the food, beverage, and agricultural industries. According to the Center for Media and Democracy, "In reality, IFIC is a public relations ...
.


Commercial activity

, interest in intermittent fasting led some companies to commercialize diet coaching,
dietary supplement A dietary supplement is a manufactured product intended to supplement one's diet by taking a pill, capsule, tablet, powder, or liquid. A supplement can provide nutrients either extracted from food sources or that are synthetic in order ...
s, and full meal packages. These companies were criticized for offering expensive products or services that were not backed by science.


See also

*
List of diets An individual's diet is the sum of food and drink that one habitually consumes. Dieting is the practice of attempting to achieve or maintain a certain weight through diet. People's dietary choices are often affected by a variety of factors, incl ...
* Sustainable diet


References


External links


The benefits of intermittent fasting
Jane E. Brody, The New York Times, 17 February 2020
Intermittent fasting
Harriet Hall, Science-Based Medicine, December 2015 {{Fad diets Diets Eating behaviors of humans Fad diets Fasting