Deliberate abstention from food appears in Jewish, Christian, Islamic, Hindu, Buddhist, Jain and numerous other traditions, in forms that differ considerably.
Independent emergence across unrelated traditions is interesting. It suggests the practice does something that people in quite different contexts kept discovering.
The variety of forms
Worth noting because generalisations obscure real differences.
Complete abstention from food and drink for defined hours, as in Ramadan. Abstention from particular categories rather than from food generally, as in various Christian and Hindu observances. Reduced quantity rather than complete abstention. Abstention on particular days of the week or month. Extended fasts undertaken by ascetics.
The variation matters because the practices are doing different things. A single day of complete abstention and a season of dietary restriction are not the same practice with different intensities.
The stated purposes
Traditions offer explicit reasons, and they cluster.
Discipline over appetite. The idea that a person governed by immediate desire cannot pursue anything requiring sustained effort, and that voluntary restraint in one area builds a capacity applicable elsewhere.
Solidarity with the hungry. Experiencing hunger deliberately as a route to understanding involuntary hunger, frequently connected to obligations of charity. In several traditions, fasting is paired explicitly with giving.
Attention. Removing a routine activity creates awareness of it. The person fasting notices how often they think about food, which is information about the ordinary state.
Preparation. Fasting before a significant observance, marking a transition and creating readiness.
Penitence. Associated with repentance and atonement in several traditions.
Purification. Understood variously as spiritual or physical, depending on the tradition.
The social dimension
Frequently underemphasised in individual-focused accounts.
Communal fasting is a shared undertaking. Everyone in a community is doing the same difficult thing at the same time, which produces something a private practice doesn't.
The shared difficulty creates identity and mutual recognition. The breaking of the fast becomes a shared celebration.
Anthropological work on ritual has proposed that costly practices — those requiring real sacrifice — function as signals of commitment, and that this contributes to group cohesion. Fasting is a straightforward example: it's difficult, it's visible, and it's undertaken together.
Which suggests that a substantial part of what fasting does is social rather than individual, and that the modern practice of fasting alone for health reasons is a different activity despite the physical similarity.
The physiological question
Fasting has become a subject of medical research, and it's worth separating that from the religious practice.
Research on intermittent fasting and time-restricted eating has examined effects on weight, metabolic markers and various outcomes. Findings are mixed, with several trials suggesting that effects on weight are largely attributable to reduced total intake rather than to timing.
Some evidence exists for metabolic effects beyond calorie reduction, and it's less established than popular coverage suggests.
The traditions were not making metabolic claims, and reading modern research back into ancient practice is anachronistic. That some religious fasting patterns resemble regimens now being studied is interesting and not evidence that either was doing what the other does.
Fasting also carries genuine risks for some people — those with diabetes, eating disorders, pregnancy, certain medications, and various conditions — and every tradition with a developed fasting practice includes exemptions, which suggests the risks were recognised.
The observation that recurs
Across traditions, one point is made repeatedly: fasting without accompanying moral change is worthless.
Prophetic criticism of ritual observance without justice appears in several scriptural traditions. The complaint is consistent — abstaining from food while treating people badly is a performance rather than a practice.
Which suggests the traditions were aware of the failure mode, and that the practice was understood as an instrument rather than an achievement.
What might transfer
For anyone outside a tradition, considering what's available.
The attention effect is real and requires no belief. Removing something routine reveals how much of your day is organised around it.
The discipline argument is plausible and less well evidenced than it's asserted. Whether restraint in one domain transfers to others is a genuine empirical question and the answer is not obviously yes.
The solidarity dimension only works if it's connected to something — the traditions pair fasting with giving for a reason, and fasting alone produces the experience without the consequence.
And the communal element cannot be reproduced individually, which may be the most significant thing lost when the practice is extracted from a tradition.
Anyone considering fasting for health reasons, particularly with an existing medical condition, should consult a healthcare professional first.
The exemptions
Worth noting because they reveal how the traditions understood the practice. Every developed fasting observance includes exemptions, and the categories are strikingly consistent across traditions.
The ill, the pregnant and nursing, children, the elderly, travellers, and those engaged in heavy physical labour are commonly exempted or given modified obligations.
That consistency suggests the practices were understood as instrumental rather than as ends in themselves. A tradition that treated abstention as intrinsically meritorious would have less reason to excuse anybody.
It also suggests practical observation. The groups exempted are broadly those for whom fasting carries genuine physiological risk, which is a conclusion the traditions appear to have reached without the physiology.