Abstinence can vary, from complete abstinence from food and drink or lighter, lower-calorie eating, fasting is practiced in a variety of religions and philosophies, including Christianity, Islam, and Hinduism.
For Muslims Ramadan is a form of intermittent fasting, a term used to describe a variety of eating patterns in which they consume nothing for periods of time that can range from 12 hours on a regular basis.
Jews, like Muslims, completely abstain from food and drink, including water, several times throughout the year.
Catholics abstain from meat on Fridays during Lent, while Greek Orthodox Christians abstain from dairy products, eggs, and meat, and occasionally olive oil and fish, for a total of 180-200 days each year.

What is religious fasting? Source: Getty Images/lacaosa