fasts

Fasts are periods during which individuals refrain from consuming all or part of food and drink for a defined time. They may be undertaken for religious, cultural, health, or personal reasons and vary widely in duration, rules, and intensity.

Religious and cultural fasting includes practices such as Ramadan, where participants abstain from food and drink from dawn to sunset; Yom Kippur, a full-day fast from food and liquids; and various community or seasonal fasts that reduce or omit certain foods. Intermittent fasting is a contemporary pattern that alternates eating and fasting windows, for example 16/8 (16 hours fast, 8 hours eating) or the 5:2 method (calorie restriction on specific days).

Medical or therapeutic fasts are usually conducted under supervision and may involve extended abstention from food or caloric intake for study or treatment purposes. Some protocols allow water but not food, while others restrict both. Prolonged or dry fasts carry higher risk and are typically not recommended without professional oversight.

Physiological effects of fasting include shifts from glucose-based to fat-based energy use, potential ketosis, and changes in hormones and metabolism. Some protocols aim to support weight loss, metabolic health, or cellular repair processes, but results vary by individual and method. The scientific evidence is mixed, and health benefits are not universal.

Safety considerations are essential. Fasts are not suitable for everyone and can cause dehydration, electrolyte imbalance, hypoglycemia, headaches, or fainting. Contraindications include pregnancy, lactation, infancy, diabetes with medication, and a history of eating disorders. When attempting a fast, hydration should be maintained where allowed, and meals should be reintroduced gradually after the fast ends.