Intermittent Fasting Calculator
Fasting: Ancient Secret, Modern Trend
Intermittent Fasting (IF) is not a diet in the traditional sense. It does not tell you what to eat; it tells you when to eat.
For thousands of years, humans evolved in environments where food was scarce. We are biologically designed to function (and thrive) during periods of fasting. It is only in the modern era of 24/7 fast food and refrigerators that we started eating every 3 hours.
By compressing your eating window, you naturally reduce your calorie intake (itās hard to overeat in 8 hours), but you also unlock metabolic benefits that constant grazing prevents.
The 4 Most Popular Protocols
Our calculator helps you plan the specific hours for the most effective fasting schedules:
| Protocol | Fast / Eat | Difficulty | Best For |
|---|---|---|---|
| 12:12 (TRF) | 12h / 12h | Easy | Beginners eliminating late-night snacking. |
| 16:8 (Leangains) | 16h / 8h | Moderate | The gold standard. Sustainable for daily life. |
| 18:6 | 18h / 6h | Hard | Accelerated fat loss and autophagy. |
| 20:4 (Warrior) | 20h / 4h | Expert | Eating one large meal. High autophagy benefits. |
The Magic of Insulin & Autophagy
Why bother fasting? Why not just cut calories?
Every time you eat, your body releases Insulin to handle the blood sugar spike. Insulin is a storage hormoneāit tells your body to store energy as fat. If you graze all day, your insulin is constantly elevated, making it chemically difficult for your body to burn stored fat.
By fasting for 16+ hours, you allow insulin levels to drop to baseline. In the absence of food energy, your body finally unlocks the fat stores.
Around the 16-18 hour mark, a cellular cleaning process begins. Your body identifies old, damaged cells and proteins and recycles them. This process is linked to anti-aging, longevity, and reduced inflammation. You cannot trigger this by calorie restriction alone; you need the absence of food.
What Breaks a Fast? (The Rules)
This is the most common question. The goal is to keep insulin low.
- Allowed: Water, Black Coffee, Unsweetened Tea (Green/Black), Sparkling Water.
- Technically Okay (Dirty Fast): A splash of heavy cream, Stevia, Zero-calorie sodas. (These may not spike insulin much, but they might trigger hunger).
- Forbidden: Sugar, Milk (Latte), BCAAs, Whey Protein, Juice, Bulletproof Coffee (Oil/Butter).
Women vs. Men: A Crucial Difference
While men usually thrive on 16:8 or OMAD (One Meal A Day), women's bodies are more sensitive to caloric restriction cues.
Extended fasting can sometimes disrupt female hormones (Kisspeptin), leading to irregular cycles. Many experts recommend women start with a gentler 14:10 approach or practice "Crescendo Fasting" (fasting only 3 days a week) to get the benefits without the hormonal stress.