Deliberate abstention from food appears so widely across religions that it invites the question of why.
Common forms
Complete abstention, restricted hours and restricted foods.
Which vary by tradition and by season.
Stated purposes
Purification, discipline, solidarity with the poor and preparation for festival.
Which are emphasised differently across traditions.
Communal dimension
Fasting observed collectively.
Which produces a social experience alongside a personal one.
Health considerations
Traditions generally exempting the ill, pregnant and elderly.
Which is a longstanding feature rather than a modern accommodation.
Ramadan
Abstention from food and drink between dawn and sunset for a lunar month.
Which is observed by very large numbers of people worldwide.
Communal meals at the start and end of the day are central to how it is experienced.
Christian traditions
Lenten practices and fasting days varying widely between denominations.
Which have generally become less strict over time.
Jewish fast days
Days of complete abstention associated with atonement and mourning.
Hindu, Jain and Buddhist practices
Fasts tied to calendars, deities and monastic rules.
Which include restrictions on timing as well as content.
Health research
Interest in intermittent fasting overlapping with these practices.
Which is a separate literature with its own limitations.
Why it is so widespread
Anthropologists have proposed several explanations: signalling commitment, building group cohesion, and marking time.
Which are not mutually exclusive and none is settled.
Traditions themselves usually give theological reasons rather than functional ones.
Feasting alongside fasting
Periods of restriction followed by celebration.
Which is a paired structure appearing very widely.
Exemptions and accommodations
Illness, pregnancy, childhood, age and travel.
Which are built into the rules rather than being concessions.
Contemporary observance
Practice varying enormously within traditions.
Which surveys consistently show.
A general note
Anyone with a medical condition should take advice before fasting; most traditions explicitly permit exemption on health grounds.
What observance looks like in practice
Households adjusting schedules, meals, work and sleep around the fast.
Which is the part that dominates the experience and rarely features in descriptions of the practice.
Employers and schools in many countries now make formal accommodations for major fasting periods.
Breaking the fast
Meals with specific foods and customs.
Which carry as much cultural weight as the abstention itself.
Fasting outside religion
Political hunger strikes and therapeutic fasting.
Which borrow the form for different purposes.
Children and young people
Gradual introduction in most traditions.
A general note
This is descriptive; medical advice matters for anyone with diabetes, an eating disorder history, pregnancy or medication requirements.
The variety within traditions
Strictness, duration and what counts as breaking a fast all differ between communities that share a tradition.
Which means generalisations about any religion's fasting practice are usually too broad.
Local custom, legal school, denomination and individual observance all produce substantial variation.
Fasting and hospitality
Obligations towards guests during fast periods.
Which traditions handle in different ways.
Public life
Workplace and school accommodations.
Which vary by country and by employer.
Scholarly study
Comparative work on ascetic practice across religions.
A general note
This is a descriptive overview and not religious guidance; each tradition's own authorities are the source for its rules.
How this article treats its subject
Everything here is written descriptively. Where a practice belongs to a living religious tradition, the aim is to say accurately what that tradition does and says about it, without arguing for or against its beliefs. Those are questions for the traditions themselves and for the people who belong to them.
Where research is mentioned, the intention is to report what studies have found rather than what enthusiasts or critics have claimed about them, including where the findings are weaker or more contested than popular coverage suggests.
Where to read further
Primary texts in good annotated translations, academic histories, and practitioners speaking about their own tradition are all more reliable than secondary summaries, including this one. Most of the traditions discussed here have extensive scholarly literature that is accessible to general readers, and university presses publish short introductory volumes on nearly all of them.
Where a practice has physical or psychological effects, medical and mental health professionals are the appropriate source of guidance, and nothing here is intended as advice of that kind.
A note on why history matters here
A great deal of contemporary spiritual and wellbeing material presents itself as ancient when it is recent, or as universal when it belongs to a particular tradition and place. Neither of those is necessarily dishonest, and both make it harder to understand what one is actually doing.
Knowing where a practice comes from, who developed it, what it was originally for and what changed along the way does not diminish it. It usually makes it more interesting, and it makes claims about it easier to evaluate.
On sources and disagreement
Scholars disagree about much of this material, sometimes sharply, and where that is the case it has been noted rather than resolved. Presenting contested questions as settled would be more comfortable to read and less accurate.