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Intermittent Fasting
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Plan your exact fasting window, see when to eat, and calculate your calorie targets for 16:8, 18:6, 5:2, and OMAD fasting protocols. 100% Free.

💡 16:8: Most popular. Fast 16 hours, eat within an 8-hour window. Great for beginners.

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How Intermittent Fasting Works

Intermittent fasting (IF) is an eating pattern that cycles between periods of fasting and eating. It doesn't specify which foods you should eat, but rather when you should eat them.

Unlike traditional diets, fasting focuses on changing the timing of your meals to optimize hormones, improve insulin sensitivity, and naturally reduce calorie intake.

The Most Popular Fasting Protocols

  • 16:8 Method (Leangains): The most sustainable and popular approach. You fast for 16 hours and eat all your meals within an 8-hour window. Often achieved simply by skipping breakfast and not eating after dinner.
  • 18:6 Method: A step up from 16:8, offering a longer 18-hour fast. This allows more time for insulin levels to drop and fat-burning to occur.
  • 20:4 Method (The Warrior Diet): You fast for 20 hours and eat one large meal (or two small ones) within a 4-hour window. This is considered advanced.
  • 5:2 Diet: You eat normally (at your TDEE maintenance calories) for 5 days of the week, and restrict your calories to 500-600 on 2 non-consecutive days.
  • OMAD (One Meal A Day): You fast for 23 hours and consume all your daily calories in a single 1-hour window. Highly restrictive.

Intermittent Fasting and TDEE: The Calorie Rule

A common misconception is that fasting allows you to eat as much as you want during your eating window and still lose weight. This is false.

Intermittent fasting does not break the laws of thermodynamics. Your Total Daily Energy Expenditure (TDEE) still dictates your weight changes. If your TDEE is 2,000 calories and you eat 2,500 calories during your 8-hour window, you will gain weight. IF works for weight loss because condensing your meals into a smaller time frame naturally makes it harder to overeat, leading to a calorie deficit.

What Breaks a Fast?

To maintain a true fasted state, you must avoid calories. Consuming the following will NOT break your fast:

  • Water (still or sparkling)
  • Black coffee (no milk, no sugar)
  • Plain green, black, or herbal tea
  • Salt / electrolytes (sugar-free)

Consuming anything with calories (even small amounts of milk, BCAAs, bone broth, or diet sodas with certain artificial sweeteners) can trigger an insulin response and break your fast.

FAQ

Fasting Questions Answered

The 16:8 protocol involves fasting for 16 hours a day and consuming all your calories within an 8-hour eating window. It is the most popular form of intermittent fasting because it easily aligns with normal sleep schedules (e.g., stopping eating at 8 PM and breaking your fast at 12 PM the next day).
No. Intermittent fasting dictates *when* you eat, not *what* you eat. Your Total Daily Energy Expenditure (TDEE) remains the same. To lose weight while intermittent fasting, you must still be in a calorie deficit.
Yes. Black coffee, unsweetened tea, and water will not break a fast. They contain zero calories and do not trigger an insulin response. Avoid adding milk, sugar, or artificial sweeteners if you want strict fasting benefits.
The 5:2 diet involves eating normally (at maintenance TDEE) for 5 days a week, and eating only 500-600 calories on 2 non-consecutive days. It works for weight loss because it creates a weekly calorie deficit. It is not necessarily 'better' than 16:8; it just depends on which schedule you find easier to stick to.