16:8 Intermittent Fasting: How to Do It

16:8 intermittent fasting sets an 8-hour eating window and a 16-hour fasting window within each 24-hour day. Use the intermittent fasting timer to track your chosen window.

What is 16:8 intermittent fasting?

16:8 is a time-restricted eating schedule: you eat during a chosen 8-hour period and avoid food during the other 16 hours. The fasting period can include the time you spend asleep.

The schedule tells you when to eat, not exactly what or how much to eat. It does not require a particular number of meals, and it does not guarantee weight loss or other health benefits.

If you are deciding whether any fasting schedule fits your circumstances, read how to start intermittent fasting first. Check the safety guidance below before trying 16:8, especially if you have a medical condition or take medication.

How do you do 16:8 intermittent fasting?

1. Choose an eating window. Pick 8 hours that work with your sleep, work, family meals, and other commitments. For example, you could eat between 10 a.m. and 6 p.m., then fast from 6 p.m. until 10 a.m. the next day. Your last meal should finish by the end of the eating window, rather than start then.

2. Plan meals that meet your needs. Arrange meals and snacks within the window in a way that leaves you satisfied and able to eat enough. Include a mix of foods, such as protein sources, vegetables or fruit, whole grains or other fiber-rich carbohydrates, and sources of unsaturated fat. You do not need to fit all your food into one meal or follow a special menu to use the schedule.

3. Stay hydrated during the fast. Plain water is appropriate during both windows unless a clinician has told you to limit fluids. Unsweetened tea and black coffee are also commonly used during a fast; added sugar, milk, or cream contributes calories. If caffeine makes you feel unwell, particularly on an empty stomach, choose water instead.

4. Ease into the timing if needed. If a 16-hour fast feels like too much of a change, you might begin with a 12-hour overnight fast and gradually adjust your eating window. There is no required pace, and you do not need to reach 16 hours if the schedule leaves you feeling unwell. A gradual start is not a workaround for a medical reason to avoid fasting.

5. Keep medication instructions intact. Take prescribed medication as directed, including any instruction to take it with food. Do not change a dose or its timing to fit a fast without checking with your prescriber or pharmacist. If your medication schedule conflicts with 16:8, ask a clinician whether fasting is appropriate for you.

6. Pay attention to daily demands. Consider how the schedule fits exercise, sleep, travel, and times when you need to concentrate. If you feel weak or dizzy during activity, stop fasting and eat or drink rather than pushing through. A different eating window, a shorter fast, or no fasting may suit you better.

7. Review whether the routine is sustainable. Notice whether you can eat enough, stay hydrated, sleep normally, and participate in meals without undue stress. You can move the window to fit your life; it does not have to be the same hours for everyone. Stop the fast if you feel unwell, and use the guidance below to decide when to seek help.

How often should you follow 16:8?

A typical 16:8 routine repeats the same pattern each day, but there is no schedule that everyone must follow. You can choose a consistent window when it fits your life, or decide that a less restrictive routine is more practical.

Missing a day or eating outside your planned window is not a reason to compensate with a longer fast. Resume a schedule that feels manageable if you want to continue, and prioritize regular meals when circumstances make fasting difficult.

If the routine repeatedly leaves you hungry, preoccupied with food, tired, or unable to eat enough, reconsider it. A pattern you can follow comfortably is more useful than forcing yourself to meet the clock.

What are the benefits of 16:8?

For some people, the main practical benefit is a predictable meal schedule. A defined window may make it easier to organize meals or reduce unplanned snacking, although other people may find the restriction inconvenient or stressful.

Weight loss is not automatic: what and how much you eat, as well as your overall circumstances, still matter. It is also possible to eat too little during a restricted window, so fitting in adequate food matters more than completing the fast.

No clinical studies are cited on this page to establish that 16:8 is better than another eating pattern or produces a particular health outcome. Do not assume it will improve blood sugar, heart health, or longevity. 16:8 is not a detox method: the liver and kidneys do most of the body's detoxification, while the lungs and gut also help eliminate waste.

What are the risks, and who should avoid 16:8?

Fasting can cause hunger, headaches, irritability, dizziness, or difficulty concentrating. Some people may find that restricting eating times makes their relationship with food more stressful or makes it difficult to meet their nutritional needs.

Children and adolescents, people who are pregnant or breastfeeding, and people with a current or past eating disorder should avoid fasting unless their clinician specifically advises otherwise. People who are underweight or frail should also speak with a clinician before considering it.

If you have diabetes, kidney disease, another ongoing medical condition, or take medication that affects blood sugar or needs to be taken with food, ask your clinician before trying 16:8. Fasting may require an individualized plan; never stop or adjust medication on your own.

Stop fasting if you feel shaky, dizzy, weak, or otherwise unwell, and eat or drink as appropriate. If you have diabetes and suspect low blood sugar, follow your prescribed treatment plan and seek medical advice if symptoms do not improve.

Seek urgent medical help for severe or persistent symptoms, confusion, or fainting. If someone is unconscious or cannot swallow safely, call emergency services and do not give them food or drink by mouth.