Why humans fast: religion, history, and the meaning of going without

Imagine trying to explain fasting to someone from a culture that has never encountered the idea. You tell them that people deliberately refuse food, sometimes even when food is plentiful. They may do this to pray, grieve, prepare for a sacred event, discipline the mind, demonstrate solidarity, or persuade a government to change its behaviour.

The listener might reasonably ask what these activities have to do with dinner.

The answer turns out to be more interesting than any single diet plan. Eating is one of the most basic human activities. Every society organizes part of its life around food, and nearly every person develops habits and desires connected to it. Refusing something so ordinary can therefore carry unusual meaning.

Fasting has appeared in different traditions for different reasons, often without a single shared origin. Ancient people didn’t know about ketones, growth hormone, or orexin. They knew what it felt like to be hungry, and they discovered that voluntarily refusing food could change the experience of attention, ritual, community, and desire.

1. From food scarcity to deliberate restraint

The biological background isn’t a spiritual explanation

Humans evolved with uncertain access to food. Harvests failed, hunting was unpredictable, travel separated people from supplies, and illness interrupted eating. These conditions help explain the body’s ability to use glycogen, fat, and ketones when no new food arrives.

But surviving involuntary scarcity isn’t the same thing as choosing a religious fast. A failed harvest is not a wellness retreat, and famine doesn’t become beneficial because modern fasting enthusiasts have discovered autophagy.

At some point, people began using food abstinence deliberately. Comparative historian Rudolph Arbesmann argued in a classic 1951 study of religious fasting that the practice appeared independently in different cultures and was not inherited from one original religion. Cultural influences and borrowings certainly occurred, but there is no single historical inventor of the fast.

Anthropologist Michael Dietler offers a useful way to think about this. Feasting and fasting both use food’s symbolic importance, one through unusual consumption and the other through intentional refusal. A feast says something by making food central. A fast says something by making its absence central.

Why food makes such a powerful symbol

We can choose not to watch television without changing the basics of survival. Food is different. It is necessary, pleasurable, social, ritualized, and closely tied to family and identity. Temporarily giving it up therefore does more than change an energy calculation.

A fast interrupts ordinary life. Meal times are noticed because meals don’t arrive. Hunger may become an occasion for prayer, mourning, or reflection. People may discover how much time is normally spent shopping, cooking, eating, cleaning up, and thinking about what comes next.

This isn’t proof that fasting creates spiritual insight. It helps explain why cultures found it a useful symbol of seriousness, self-restraint, grief, or devotion.

2. Judaism, Christianity, and Islam: fasting before God

Judaism: atonement and remembrance

In Judaism, fasting can express repentance, communal mourning, and remembrance. Yom Kippur, the Day of Atonement, is the central example, involving a day devoted to reflection and repentance and a fast lasting from before sundown to after nightfall. Tisha B’Av commemorates major catastrophes in Jewish history, especially the destruction of the Temples in Jerusalem. Other fasts mark additional historical events.

The important point is not that a particular fast reliably improves blood glucose. It is that ordinary pleasures are interrupted to make room for an ethical and spiritual task. A day devoted to accountability feels different when the usual comforts are temporarily unavailable.

Jewish commentary also recognizes tensions in fasting. The fast may serve the religious purpose, but concern for health and preservation of life remain important. Jewish traditions do not reduce spiritual seriousness to the ability to endure physiological harm.

Christianity: repentance, preparation, and the danger of pride

Christianity inherited and developed fasting traditions associated with prayer, repentance, charity, and preparation. The Gospels describe Jesus fasting in the wilderness, and early Christian communities practiced fasting before significant religious observances.

The forty-day season associated with Lent became established in the early Church. Yet “forty days of fasting” generally did not mean forty days of drinking water and eating nothing. As the Greek Orthodox Archdiocese’s history explains, longer seasonal fasts developed into forms of ascetic restriction involving foods such as meat, dairy, and eggs, alongside other practices of worship and self-restraint.

The distinction matters because modern people sometimes read historical fasting accounts as if every monk had signed up for a twenty-one-day water-only challenge. Religious observances were often far more varied—and not designed around modern definitions of ketosis.

Early monastic tradition also contains a revealing argument about the danger of excessive asceticism. Severe deprivation can become a performance. Someone who begins fasting to weaken attachment may find themselves attached to the identity of being exceptionally good at fasting. The ego is perfectly capable of turning an empty plate into an achievement certificate.

Different Christian communities now maintain very different expectations. Eastern Orthodox fasting remains extensive and often food-specific. Catholic practice includes defined days of fasting and abstinence. Many Protestant communities emphasize voluntary observance rather than a uniform calendar.

The shared theme is not nutritional uniformity. It is the use of restraint to redirect life toward spiritual commitments.

Islam: a community reorganized around Ramadan

Ramadan provides one of the world’s most visible fasting traditions. Adult Muslims who are required to fast abstain from food and drink from dawn until sunset, then eat and hydrate during the night. The Qur’an, in chapter 2, connects the practice with righteousness or God-consciousness and describes accommodations for illness and travel.

The fast is not simply an individual test of hunger. Daily routines change. Meals become communal occasions, and the act of breaking the fast carries a special social and religious meaning. Food is not rejected as evil; its timing is transformed by the sacred calendar.

Scientifically, Ramadan also reminds us why the word fasting covers different realities. Day length changes with latitude and season. Sleep schedules, total food intake, and nighttime hydration vary. A short winter daylight fast is metabolically different from an unusually long summer daylight fast, even though both belong to the same religious observance.

A modern study of eight volunteers found increased orexin-A during daytime fasting hours. That offers a possible piece of the physiology behind altered wakefulness. It does not establish that orexin causes religious devotion, and reducing Ramadan to a hormone experiment would miss its central purpose.

3. Buddhism, Hindu traditions, Jainism, and Daoism

Buddhism: the Middle Way and the timing of meals

The Buddhist story is especially interesting because early teachings explicitly reject the idea that extreme bodily deprivation automatically produces wisdom. The Buddha is traditionally described as having tried severe asceticism before turning toward the Middle Way.

Yet food restraint remained part of monastic discipline. In Theravada practice, monks traditionally take food between dawn and noon and abstain from solid food during the afternoon and night. Some lay Buddhists undertake similar restrictions during periods of intensified observance.

This is a daily discipline of appetite rather than a claim that starvation itself produces enlightenment. The meal schedule can simplify monastic life, reduce preoccupation with food, and support meditation and study. The larger question concerns attachment: can a desire arise without demanding obedience?

That is not the same thing as pretending hunger doesn’t matter. Buddhism’s rejection of extreme asceticism is a warning against confusing needless suffering with insight.

Hindu traditions: fasting as a vow

Hindu practices are too varied to collapse into a single fasting rule. Across regions and communities, observances may involve avoiding particular foods, eating only once, fasting on designated lunar days, or making vows associated with particular deities and festivals.

The Sanskrit concept of vrata is useful here. Historian Tracy Pintchman describes these as religious observances or vows with specific intentions and ritual forms. Fasting may be part of a vow, but its significance depends on the devotion, promise, and context rather than merely the absence of calories.

Hindu ascetic traditions also include more demanding renunciatory practices. Some emphasize discipline, others devotion, others the pursuit of liberation. It would be a mistake to describe all of these as one ancient nutritional theory.

Jainism: abstinence and non-attachment

Jainism places especially strong emphasis on nonviolence, restraint, and renunciation. Anthropologist James Laidlaw has described fasting as a prominent expression of Jain ascetic practice, embedded in vows and broader moral commitments. Fast lengths and food restrictions vary among monastics and lay practitioners.

At the most extreme end is sallekhana, an exceptional end-of-life practice involving progressive renunciation of food and eventually death under particular religious conditions. It is the subject of serious ethical and legal debate, not a wellness technique to imitate. Including it illustrates how differently a culture may understand deliberate food refusal, not an endorsement of the practice.

The shared Jain theme is that appetite and attachment can be linked: learning not to obey every desire may have moral or spiritual significance. That idea appears in many traditions, although they disagree about what it ultimately means.

Daoism: fasting the mind

Some Daoist traditions developed dietary restraint and grain-avoidance practices associated with purification or longevity. But the most philosophically interesting form of fasting may involve no actual food restriction at all.

The Zhuangzi describes xinzhai, often translated as the “fasting of the mind” or “fasting of the heart-mind.” It concerns loosening habitual judgments and becoming receptive rather than filling every experience with predetermined ideas. It is not an instruction to stop eating until a particular ketone concentration is achieved.

The metaphor works because fasting means removing something that is ordinarily being consumed. The stomach can consume food; the mind can consume explanations, expectations, grievances, and endless commentary.

That thought deserves a separate article of its own. It also offers a useful counterweight to the temptation to turn spiritual life into another optimization protocol. A person can spend so much effort perfecting the fasting schedule that they forget to notice what fasting was supposed to reveal.

4. When fasting became medicine—and politics

From ancient regimens to ketogenic diets

Fasting has long been associated with healing, including in Greek medical traditions that treated diet and daily regimen as important tools. Ancient claims about particular diseases should not be confused with modern evidence, and famous quotations attributed to Hippocrates are often repeated with uncertain sourcing.

One modern medical development, however, has a clear history. During the early twentieth century, fasting was used experimentally in epilepsy treatment. In 1921, physician Russell Wilder proposed that if fasting helped some seizures through increased ketones, perhaps a high-fat, very-low-carbohydrate diet could reproduce part of that metabolic state without requiring prolonged food deprivation.

This helped establish the ketogenic diet as a treatment for epilepsy. A 2019 historical review by Sophie Höhn and colleagues reconstructs Wilder’s reasoning and the rapid expansion of ketogenic-diet research during the 1920s.

The result is an unusually good example of a fasting observation being transformed into something more sustainable: rather than requiring patients to stop eating indefinitely, researchers looked for a way to reproduce selected metabolic effects while still providing nutrition.

The diet’s therapeutic mechanism is more complex than ketones alone, and modern ketogenic dietary therapies are used under medical guidance for particular forms of epilepsy. But the history shows how fasting generated a productive medical hypothesis without requiring the claim that fasting itself cures every neurological condition.

Gandhi and the fast as public speech

Fasting also became a form of political action. Mohandas Gandhi used it in conjunction with nonviolent resistance, self-discipline, and moral persuasion. His fasting was connected with wider ideas about personal conduct, sacrifice, communal responsibility, and satyagraha.

Philosopher Gail Presbey’s account of Gandhi’s methods places fasting among civil disobedience, boycotts, strikes, and voluntary imprisonment. It could be politically powerful precisely because refusal of food is costly and visible.

But fasting as persuasion creates an ethical tension. One person may see self-sacrifice and moral appeal; another may see pressure placed on others through the threat of self-harm. The fact that fasting can communicate sincerity does not settle whether every political use is justified.

Again, the body is doing something physiologically recognizable. The meaning attached to it is a separate human construction.

5. Why does fasting keep appearing?

Hunger can interrupt autopilot

Our normal response to hunger is to eat. That is usually sensible. But because the response is so automatic, we rarely observe the sensation for long. We don’t necessarily notice how it builds, changes, and sometimes subsides, or how strongly it follows the clock rather than an immediate energy emergency.

Fasting interrupts that sequence. It creates a space between an urge and a response. Religious traditions have used that space for repentance, study, prayer, mourning, or self-observation. These are different goals, but they all rely to some extent on food being important enough that its temporary absence changes the day.

Someone can use that interval thoughtfully. Someone else can spend it thinking about sandwiches from morning to night. Nothing about the biological state guarantees contemplation.

Is orexin part of the prayer experience?

We know from physiology that fasting can affect arousal systems, including orexin neurons involved in wakefulness and food-seeking. It’s possible that in certain circumstances this contributes to experiences of wakefulness or attentional intensity during religious practice. But a plausible mechanism is not a demonstration that fasting improves prayer or produces unusual awareness in everyone.

The distinction protects both science and religion from an odd kind of overconfidence. Modern scientists need not claim they have measured spiritual insight in a blood sample. Religious historians need not pretend that monks understood hypothalamic peptides.

What can be said is simpler: people noticed that the deliberate absence of food changes experience, and they gave that experience different meanings according to their traditions.

Restraint in an age of abundance

Historical fasting often occurred against a background where involuntary scarcity was a real possibility. Modern Western fasting often occurs in the opposite setting. Food is available at nearly every hour. We can order dessert without leaving a chair, and the refrigerator lights up helpfully when we open it at midnight.

In that environment, deliberately not eating can feel surprisingly radical. It interrupts an ordinary assumption: that because something is available and desirable, we should immediately have it.

That is an interesting insight, but it doesn’t require anyone to prove their spirituality with a twenty-one-day water fast. Many religious traditions themselves distinguish useful discipline from self-destructive excess.

6. The strange human practice of not eating

An animal that is hungry usually searches for food. Humans sometimes do something stranger: we become hungry on purpose, and then give the hunger a meaning. We use it to pray, remember, repent, protest, undertake a vow, or examine our habits.

There is no single reason fasting appears so often across cultures. Its physical simplicity and the importance of food make it available as a form of symbolism almost everywhere. The theology and social meaning vary enormously.

The mistake would be to treat ancient religious practice as proof of a modern medical theory. People didn’t need to know about glycogen or autophagy to discover that hunger changes attention. Their experience may have been genuine while their explanations differed from the laboratory’s explanations—and while the clinical value of prolonged fasting remains uncertain.

The best question to carry away from this history may not be how many hours we should go without food. It may be what becomes visible when an ordinary habit is temporarily removed.

Research and references

• Arbesmann R (1951), Fasting and prophecy in pagan and Christian antiquity, Traditio: https://doi.org/10.1017/S0362152900015117
• Dietler M (2012), Feasting and fasting, Oxford Handbook of the Archaeology of Ritual and Religion: https://doi.org/10.1093/oxfordhb/9780199232444.013.0014
• My Jewish Learning, History of Yom Kippur: https://www.myjewishlearning.com/article/history-of-yom-kippur/
• Greek Orthodox Archdiocese, Fasting in Orthodox Christian tradition: https://www.goarch.org/-/not-by-bread-alone-fasting-today-in-the-orthodox-christian-way
• Qur’an, Surah al-Baqarah 2:183–185 (translation): https://legacy.quran.com/2/183-186
• The Bhikkhus’ Rules, meal timing in Theravada monastic practice: https://accesstoinsight.org/lib/authors/ariyesako/layguide
• Pintchman T (2020), Women’s observances: Vratas, Oxford History of Hinduism: https://doi.org/10.1093/oso/9780198733508.003.0014
• Laidlaw J (1995), Fasting: Scorched earth and fertile soil, Riches and Renunciation: https://doi.org/10.1093/oso/9780198280316.003.0010
• Sethi M (2019), Ritual death in a secular state: Jain sallekhana: https://doi.org/10.1080/19472498.2019.1609261
• Matthyssen M (2025), The “fasting of the heart” (xinzhai): Zhuangzi, Daoism and its transformative healing power in contemporary psychotherapy: https://doi.org/10.1177/10892680241306052
• Höhn S et al. (2019), History of dietary treatment from Wilder’s hypothesis: https://pubmed.ncbi.nlm.nih.gov/31677579/
• Presbey G (2022), Mohandas Gandhi, Oxford Handbook of Peace History: https://doi.org/10.1093/oxfordhb/9780197549087.013.25
• Almeneessier AS et al. (2018), Diurnal intermittent fasting and orexin-A: https://pubmed.ncbi.nlm.nih.gov/29387256/

Medical note

This series is educational journalism, not personalized medical advice or a protocol for extended fasting. Prolonged fasting can have serious risks, particularly with chronic illness, certain medications, malnutrition, or abnormal electrolytes, and warrants professional medical supervision.