Fasting Tracker guide
16:8 intermittent fasting schedule: times, tips and safety
On a 16:8 schedule you eat all your food inside an 8-hour window, such as 12pm to 8pm, and have only water or other calorie-free drinks for the other 16 hours. Most of the fast happens while you sleep. It suits some healthy adults, but it is not for everyone, and the evidence says it works about as well as other ways of eating less, not better.
What 16:8 means
16:8 is a form of time-restricted eating. The two numbers are hours: 16 hours without food, then an 8-hour eating window, every day or on the days you choose. You don't count anything inside the window. The structure is simply when you eat.
The fast starts when you finish your last food of the day, not when you go to bed. If dinner ends at 8pm, a 16-hour fast ends at 12pm the next day. Around eight of those hours pass while you are asleep, which is why many people find 16:8 easier than it sounds.
Worked example
Last bite of dinner: 7:30pm. Sixteen hours later is 11:30am. So the eating window runs from 11:30am to 7:30pm.
A late snack at 9pm moves the whole thing: the fast would then end at 1pm. A fasting timer that starts when you actually stop eating keeps this honest.
Sample 16:8 schedules
Pick the window that fits your day, not the one that looks best on paper. You are more likely to stick to it if it lines up with work, family meals and exercise.
| Eating window | Fasting | Suits |
|---|---|---|
| 12pm to 8pm | 8pm to 12pm | The most common. Skip breakfast, keep lunch and dinner. |
| 11am to 7pm | 7pm to 11am | Earlier dinners, a late-morning first meal. |
| 10am to 6pm | 6pm to 10am | People who are hungry in the morning but can stop early. |
| 8am to 4pm | 4pm to 8am | Early risers. Hard if you eat with family in the evening. |
| 1pm to 9pm | 9pm to 1pm | Late shifts and late family meals. |
You don't have to fast every day. Some people do 16:8 on weekdays and eat normally at weekends. Gentler versions exist too: 12:12 (a 12-hour overnight gap) or 14:10. In Fasting Tracker you can switch between 12:12, 14:10, 16:8, 18:6 and others at any time.
What to eat and drink
During the fast, stick to drinks with no or almost no calories:
- Water, still or sparkling. Drink regularly, because some of the water you normally get comes from food.
- Black coffee and plain tea, including herbal tea.
- Nothing with sugar, juice, milk or cream if you want a strict fast. A splash of milk is a small amount of energy; whether it matters is your call.
Inside the window, eat normal, balanced meals. A shorter window is not a licence for anything, and it does not mean you need special foods. The NHS Eatwell Guide is a good reference: plenty of fruit and vegetables, wholegrain starchy foods, protein such as beans, fish, eggs or meat, and some dairy or alternatives.
- Break the fast with a proper meal, not a sugary snack.
- Include protein and fibre at each meal. They help you feel full for longer.
- Don't try to "fit in" extra food before the window closes.
How to start, step by step
- Check it's right for you. Read the who should not fast section first. If you take medication or have a health condition, speak to your GP or doctor before you start.
- Start with 12:12. Stop eating after dinner and have breakfast 12 hours later. Do this for a few days.
- Move to 14:10. Push your first meal back or bring dinner forward by an hour each.
- Try 16:8. Once 14 hours feels comfortable, stretch to 16. Choose a window from the table above.
- Start the timer when you stop eating. If you forget, set the start time afterwards. Fasting Tracker lets you change the start or end time of a fast.
- Review after two weeks. How do you feel, sleep and train? If it isn't working for you, stop. Fewer fasting days, or a shorter fast, are fine.
What the evidence says
16:8 is popular, but the research is more modest than many headlines suggest.
- A 12-week trial in JAMA Internal Medicine (Lowe and others, 2020) compared 16:8 eating (12pm to 8pm) with three meals a day. Time-restricted eating on its own was not more effective for weight loss.
- A 12-month trial in the New England Journal of Medicine (Liu and others, 2022) gave both groups the same calorie target. Adding an 8-hour eating window did not lead to significantly more weight loss than cutting calories alone.
- Harvard's Nutrition Source review of intermittent fasting concludes it is unclear that it is better than other weight loss methods, and that more long-term studies are needed.
So the fair summary is: 16:8 can help some people eat less, mainly because a shorter window makes it harder to snack late. It is a structure, not a shortcut. If a regular meal pattern works better for you, that is a perfectly good choice.
Who should not fast
Intermittent fasting is not safe or suitable for everyone. Don't try 16:8 without medical advice if you:
- are pregnant or breastfeeding
- are under 18, or still growing
- have diabetes, especially if you use insulin or other medicines that lower blood sugar
- have, or have had, an eating disorder
- take medicines that need to be taken with food
- are underweight, frail, or have a long-term health condition
Harvard's review lists most of these: diabetes, eating disorders, medicines that need food, growth stages such as adolescence, and pregnancy or breastfeeding. If any of them apply to you, talk to your GP, doctor or dietitian first.
Common mistakes
- Going straight to 16 hours. Building up from 12:12 is easier and tells you how your body reacts.
- Not drinking enough. Thirst can feel like hunger. Keep water to hand during the fast.
- Overeating in the window. Two huge meals can cancel out the point. Eat normal portions.
- Sweet drinks during the fast. Juice, sweetened coffee and milky drinks all contain energy.
- Treating a missed day as failure. A birthday dinner or a bad night's sleep is fine. Pick it up the next day, or don't.
- Pushing through warning signs. Feeling faint or unwell is a reason to eat, not to finish the fast.
Questions
Does sleep count towards the 16 hours?
Yes. The fast runs from your last food to your next, so the hours you sleep are part of it. With a 12pm to 8pm window, around eight of the 16 hours are usually spent asleep.
Can I drink coffee while fasting?
Black coffee and plain tea have almost no calories, so most people include them during the fast. Sugar, syrups, milk and cream add energy. If caffeine makes you jittery on an empty stomach, switch to water or herbal tea.
Do I have to do 16:8 every day?
No. Some people fast on weekdays only, or a few days a week. A shorter gap such as 12:12 or 14:10 is also fine. The best schedule is one you can keep without feeling unwell.
Will 16:8 help me lose weight?
It can help some people eat less, but trials have found it works about as well as other ways of cutting calories, not better. What you eat in the window still matters. This is general information, not medical advice.
What if I feel dizzy or unwell while fasting?
Stop the fast and eat something. Feeling faint, shaky or unwell is a sign to eat, not to push on. If it keeps happening, or you have a health condition, speak to your GP or doctor.
Is 16:8 safe if I take medication?
Check with your doctor or pharmacist first. Some medicines need to be taken with food, and medicines for diabetes can cause low blood sugar if you don't eat.