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Circadian & Fasting Scheduler

Intermittent Fasting Calculator

Calculate your exact daily fasting and eating windows across popular protocols (16:8, 18:6, 20:4, OMAD, or custom schedules). Features a live real-time countdown timer tracking your active phase.

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Understanding Intermittent Fasting Protocols

Intermittent fasting (IF) is an eating pattern that cycles between periods of fasting and eating. Rather than restricting specific foods, intermittent fasting focuses on when you eat. Popular schedules include:

  • 16:8 Protocol: Fast for 16 hours overnight/morning and eat during an 8-hour window (e.g. 12 PM to 8 PM).
  • 18:6 Protocol: Fast for 18 hours and eat within a 6-hour window (e.g. 1 PM to 7 PM).
  • 20:4 (Warrior Diet): Fast for 20 hours with a condensed 4-hour eating window.
  • OMAD (23:1): One Meal A Day protocol featuring a 23-hour fast and a 1-hour eating window.

Hydration and Fasting Rules

To remain in a fasted state, it is essential to avoid calories during your fasting window. Non-caloric beverages such as water, plain sparkling water, black coffee, and unflavored tea are permitted and encouraged to maintain proper hydration and electrolyte balance.

Frequently Asked Questions (FAQ)

What is the 16:8 intermittent fasting schedule?

The 16:8 protocol involves fasting for 16 consecutive hours overnight and during the morning, followed by an 8-hour eating window during the day (for example, eating between 12:00 PM and 8:00 PM).

What can I consume during fasting hours?

During fasting hours, you can consume zero-calorie beverages such as plain water, sparkling water, black coffee (without cream or sugar), and unflavored herbal or green tea.

How does the live countdown timer work?

Our live countdown timer updates every second based on your current device clock, calculating the exact hours, minutes, and seconds remaining until your next fasting or eating phase transition.

What is OMAD (23:1 fasting)?

OMAD stands for One Meal A Day. It consists of a 23-hour fasting period followed by a single 1-hour eating window where all daily caloric and nutrient intake is consumed.

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