Lifestyle
Food & Nutrition
FitnessGet your fasting and eating window times for 16:8, 18:6, and more.
This tool is for general information only and is not medical advice. Talk to a healthcare professional about results that concern you.
How Intermittent Fasting Works
Intermittent fasting does not tell you what to eat; it tells you when. You compress your eating into a daily window and fast the rest of the time, drinking water, black coffee, or plain tea. Pick your plan and the time you finish dinner, and this calculator hands you your exact fasting and eating windows.
Which Schedule Should You Start With?
- 14:10: the gentle entry point. Finish dinner by 8 pm, eat again at 10 am. Most people barely notice it.
- 16:8: the most popular and most studied schedule. In practice it usually means skipping breakfast.
- 18:6 and 20:4: tighter windows for experienced fasters. Harder socially, and harder to fit enough protein.
- OMAD: one meal a day. Simple in theory, demanding in practice, and not a beginner move.
Honest science note: controlled trials show intermittent fasting works about as well as ordinary calorie counting for fat loss, not better. Its real advantage is that many people find a time rule easier to follow than a counting rule. Fewer eating hours usually means fewer calories without the arithmetic. If you want to know what your body needs inside the window, the calorie calculator and protein calculator fill that in.
Fasting is not for everyone. Skip it if you are pregnant or breastfeeding, have a history of eating disorders, are under 18, or take blood sugar medication, unless your doctor says otherwise.
Frequently Asked Questions
What breaks a fast?
Anything with meaningful calories. Water, black coffee, plain and herbal tea are fine. Milk, sugar, juice, and most “zero” drinks with cream do break it. A splash of milk is a gray zone; purists skip it, pragmatists do not worry.
Can I drink coffee while fasting?
Yes, black. It even blunts appetite for many people. Watch the timing though: caffeine within 8 hours of bed costs sleep, and bad sleep sabotages fasting discipline. Our caffeine calculator covers your daily limit.
Will fasting slow my metabolism?
Daily time-restricted eating does not meaningfully lower metabolic rate in studies. Metabolic slowdown comes from prolonged large calorie deficits and muscle loss, which is a reason to keep protein high whatever schedule you follow.
Why am I not losing weight with 16:8?
The window only works if it reduces total calories. Big enough meals and snacks inside 8 hours can fully replace what breakfast used to add. Track honestly for two weeks; the answer is usually there.
Sources
- Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical Trial · PubMed Central (NIH/NLM)
- Research on intermittent fasting shows health benefits · NIH National Institute on Aging
- Intermittent Fasting: What It Is, Benefits and Schedules · Cleveland Clinic
- 8-hour time-restricted eating linked to a 91% higher risk of cardiovascular death · American Heart Association
This tool is for general information. If you have any medical condition or take medication, talk to your doctor before fasting.