Find your fasting & eating windows based on your schedule and goal
⏰ 6 Protocols🎯 Goal Based📊 All Experience Levels
⚠️ Important Safety Warning — Please Read First
Intermittent fasting is not suitable for everyone. Do not start any fasting protocol if you:
Have diabetes (Type 1 or Type 2) or blood sugar issues
Are pregnant or breastfeeding
Have a history of eating disorders
Take regular medication that must be taken with food
Have low blood pressure, kidney disease, or liver disease
Are under 18 or are underweight
🩺 Special Note for Diabetics
If you have diabetes, fasting can cause dangerous drops in blood sugar (hypoglycemia), especially if you take insulin or certain oral medications. The timing of your meals is directly tied to your medication schedule. Always consult your doctor before changing your eating schedule. If your doctor approves fasting, the 14:10 Gentle Fast is generally the safest starting point.
🎯 Which Protocol Is Right For Me?
Answer 2 quick questions and we'll recommend the best starting point
Have you tried intermittent fasting before?
Choose Your Protocol
Select the fasting method that fits your lifestyle
16:8
Leangains
Most popular & beginner friendly
Most Popular
18:6
Warrior Light
Faster results, more discipline
20:4
Warrior
Advanced — one main meal
Advanced
14:10
Gentle Fast
Great for beginners & women
Beginner Friendly
5:2
5:2 Diet
Normal eating 5 days, 500 cal x 2
OMAD
One Meal
One meal per day — extreme
Extreme
Your Eating Window Start
What time do you want to start eating each day?
Your Primary Goal
We'll show you the benefits most relevant to you
What Is Intermittent Fasting?
Intermittent fasting (IF) is an eating pattern that cycles between periods of fasting and eating. Unlike traditional diets that focus on what you eat, intermittent fasting focuses on when you eat. During fasting windows your body shifts from burning glucose for energy to burning stored fat — a metabolic state that has been linked to weight loss, improved insulin sensitivity, reduced inflammation, and even cellular repair through a process called autophagy.
The most popular intermittent fasting protocol is the 16:8 method — fasting for 16 hours and eating within an 8-hour window. Other popular approaches include 18:6, 20:4, and the more challenging one meal a day (OMAD) protocol. The right protocol depends entirely on your goals, your schedule, and your experience with fasting.
The Body HQ Intermittent Fasting Calculator takes your eating window preferences and calculates your exact fasting start and end times across 6 different protocols. It also includes a personalized recommendation quiz to help beginners find the right starting point, and important safety guidance for people who should consult a doctor before fasting.
How the Fasting Calculator Works
1
Take the recommendation quiz — if you are new to fasting, answer 2 quick questions and the calculator will recommend the best protocol for your experience level and goals.
2
Choose your protocol — select from 6 protocols ranging from the gentle 14:10 fast all the way to OMAD (one meal a day). Each protocol shows your fasting and eating hours.
3
Set your eating window start time — enter the time you want to break your fast (your first meal of the day) and the calculator works out everything else.
4
Get your schedule — see your exact fasting window, eating window, and recommended meal times displayed clearly on a visual timeline.
5
Read the protocol guide — each protocol includes a description, difficulty level, and who it is best suited for to help you make the right choice.
Frequently Asked Questions
Which intermittent fasting protocol is best for weight loss?
The 16:8 protocol is the most studied and most effective for sustainable weight loss for most people. It creates a calorie deficit by limiting eating to an 8-hour window while remaining practical enough to maintain long term. More restrictive protocols like 18:6 or 20:4 may produce faster results but are harder to sustain. The best protocol is always the one you can stick to consistently.
Can I drink coffee or tea while fasting?
Black coffee and plain tea do not break a fast and are generally considered acceptable during fasting windows. They contain minimal to no calories and may even enhance the fat-burning effects of fasting. However adding milk, cream, sugar, or sweeteners does break a fast. Plain water, sparkling water, and black coffee or tea are your best options during fasting hours.
Is intermittent fasting safe for diabetics?
Intermittent fasting can be dangerous for people with diabetes without medical supervision. Fasting can cause blood sugar levels to drop dangerously low (hypoglycemia), especially for people taking insulin or certain oral diabetes medications. If you have Type 1 or Type 2 diabetes, you must consult your doctor before attempting any fasting protocol. Your medication timing may need to be adjusted alongside any changes to your eating schedule.
What is autophagy and when does it start during fasting?
Autophagy is a cellular cleaning process where your body breaks down and recycles damaged cell components. Research suggests autophagy begins to increase after approximately 16 to 18 hours of fasting, which is one reason many people choose the 16:8 or 18:6 protocols. However the exact timing varies between individuals based on factors like metabolic health, activity level, and what was eaten before the fast began.
Will intermittent fasting cause muscle loss?
When done correctly, intermittent fasting should not cause significant muscle loss. The key is consuming adequate protein during your eating window — aim for 0.7 to 1 gram of protein per pound of body weight — and continuing resistance training. In fact some studies suggest that fasting combined with resistance training can improve body composition by reducing fat while preserving or even building muscle.
What should I eat when breaking my fast?
Breaking your fast with easily digestible whole foods is ideal. Good options include eggs, Greek yogurt, fruits, vegetables, lean proteins, and whole grains. Avoid breaking your fast with large amounts of processed food, refined sugars, or very high-fat meals — your digestive system is more sensitive after a fasting period and blood sugar spikes are more pronounced. Start with something moderate and give your body 30 minutes before eating a larger meal.
⚕️ Medical Disclaimer: Intermittent fasting is not suitable for everyone. Do not attempt any fasting protocol if you are pregnant, breastfeeding, have a history of eating disorders, take regular medication, have diabetes, or have any chronic health condition without first consulting your doctor. This calculator is for general educational purposes only and is not a substitute for professional medical advice.
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