Summary of the different fasting practices in major world religions* (reproduced based on10, with permission)
| Religion | Form of fasting |
| Islam | It is obligatory for Muslims to fast the month of Ramadan (30–31 days) which consists of no food or drink from dawn to sunset. Muslims also commonly fast the first 10 days of the Islamic lunar month Dhul-Hijjah and some Muslims commonly fast the Monday and Thursday of each week and/or the middle 3 days of each fast.49 |
| Christianity | Catholic Christians abstain from eating meat, but not fish, on Fridays in the 6-week period before Easter, called Lent. Many Catholics also only eat one full meal a day on the days of Ash Wednesday, the first day of Lent, and Good Friday.49 Some Protestants observe Lent by abstaining from certain favourite foods or habits such as smoking. A similar method of fasting is the ‘Daniel fast’ which lasts 21 days.49 The Eastern Orthodox church has different fasting periods exist including Lent as well as the Nativity fast, Apostles’ Fast and Dormition Fast. These are often several weeks long and entail fasting from specific food items such as red meat and poultry and sometimes fish, oil and wine. None of the major denominations in Christianity prohibit taking medications while fasting.49 |
| Judaism | There are several days of fasting in Judaism. These include Yom Kippur, Tisha B’Av, the Fast of Gedalia, the Tenth of Tevet, the Seventeenth of Tammuz and the Fast of Esther. These are single days of fasting from all forms of eating and drinking during this period—with the exception of Yom Kippur and Tisha B’Av where Jews abstained from all oral intake (including water) for 24 hours (from sunset to sunset). Historically, reform Jews only observed the Yom Kippur fast while Orthodox Jews the above-mentioned fasts. According to Jewish Law, important and/or regular medications can be taken with drink, and if necessary, with food as well but a patient’s medications should be reviewed by a healthcare professional to ensure the fast as compliant as possible.49 |
| Hinduism | Fasting takes many forms from abstaining from meat to only drinking water and milk. The most common fast in Hinduism is Ekadasi, which takes place twice a month and often consists of eating only fruits, vegetables and milk products (although a small minority abstain from all eating and drinking for 24 hours). Many Hindus also fast during the month of Shravan. Hindus are permitted to take medications while fasting.49 |
| Buddhism | Lay Buddhists fast by abstaining from meat and certain types of food such as processed foods, two or more times per month. Some Buddhists stop eating after midday every day and some monks go further by abstaining from food for 18 days, drinking only a small portion of water (Lee et al 2009). |
| Sikhism | Sikhism does not promote fasting except for medical reasons.49 |
| Baha’i | Fasting is observed from sunrise to sunset during the Baha’I month of ‘Ala with the complete abstention of food and drink. Patients are permitted to take medications while fasting.49 |
*Religious practice is heterogeneous. While certain fasting practices are mentioned, patients may not practise them or may practise them in a manner dissimilar to that described above.