Getting started with intermittent fasting can be confusing, especially when deciding on your fasting frequency. So, how often should you fast? There are many options to try, but determining the best frequency for you takes trial and error.
Understanding how each approach works and being aware of certain factors will help you determine what’s best.
Fasting Overview
Simply put, fasting is when an individual stops eating completely or almost completely for a certain period. In intermittent fasting, a person fasts for less than a day or more per week during which they consume between 0 and 800 calories (*).
Fasts typically last between 13 and 24 hours, but some may last longer. In many cases, zero-calorie beverages such as coffee, water, or tea are permitted during the fasting period.
Fasting is not a new way of eating. It has been and continues to be a common practice in most religious traditions, including Christianity, Buddhism, Islam, Hinduism, and Judaism.
Today, it has become a very popular method of timing meals to attain certain health and weight loss goals. Research has shown that intermittent fasting helps with body weight control, improving blood sugar levels, and lowering inflammation (*).
There are several ways to do fasting, each of which is based on choosing regular periods to eat and fast. For example, you may eat during an eight-hour window and fast for the remaining 16 hours daily. Others might eat only one meal a day, twice a week.
Important: Regardless of your desired fasting schedule, keep in mind that longer fasting periods are not necessarily better.
How Often Should You Fast?
There are different ways to fast, and how often you do each approach may vary. Here are the different fasting intervals that are typically followed and their recommended frequency:
| Fasting Duration | Fasting Frequency |
| 13-Hour Fast | The 13-hour fast involves fasting for 13 hours daily and eating within a 13-hour window. People often include their sleeping hours as part of the 13-hour fast window.
You can do a 13-hour fast daily. |
| 16-Hour Fast (16:8) | A 16-hour fast, often called 16:8 intermittent fasting, means fasting for 16 hours and eating for 8 hours. Like the 12-hour fast, most people include their sleeping time in their 16-hour fast period.
You can do a 16-hour fast daily. |
| 18-Hour Fast (18:6) | The 18:6 time-restricted eating method involves fasting for 18 hours and limiting all caloric intake to the remaining 6 hours.
You can fast for 18 hours once or twice per week. |
| 20-Hour Fast (20:4) | The 20:4 fasting method involves fasting for 20 hours and then only eating during the 4-hour window.
You can fast for 20 hours once or twice per week. |
| 24-Hour Fast | 24-hour fasting involves abstaining from all calorie sources for 24 hours.
You can fast for 24 hours once or twice per week. |
| 36-Hour Fast | Also called the Monk Fast, the 36-hour fast means abstaining from calories over the prescribed period. During the fast, you’re allowed to consume zero-calorie drinks, such as black coffee and tea, besides water.
You can fast for 36 hours only once a week. |
Factors to Consider When Determining Fasting Frequency
There are several factors to consider when deciding how often you will fast. These include but are not limited to the following:
- Your current eating schedule
- Fasting experience
- Health conditions (e.g., diabetes, hypertension, and heart disease)
- Current weight
- Fitness goals (e.g., losing fat, building muscle, or both)
- Age
- Gender
- Your activity level
Except for individuals with an existing medical condition, the two factors often considered when choosing an optimal fasting frequency are fasting experience and fitness goals. Here’s why:
When it comes to a person’s fasting experience, shorter intervals, such as the 13-hour fast, are best for beginners. 18-hour fasts and beyond are quite advanced and should be done by those who already have plenty of fasting experience. Starting with short fasts allow you to get used to going without food. The more fat-adapted you are, the easier it will be to extend your fasting hours.
Deciding to lose weight? Many people start intermittent fasting for weight loss, and indeed, this method of eating has been shown to be effective (*). Short fasts and long fasts are equally beneficial for weight loss.
If you’re more comfortable with a short fast, you might want to consider doing it more often each week — for instance, four 13-hour or 16-hour fasts per week. In case you want a longer fast, it’s also helpful to be aware that prolonged fasts might encourage your body to store fat as a result of starvation (*).
Frequently Asked Questions
Here are some commonly asked questions regarding how long one should fast:
What is the recommended fasting frequency for beginners?
For beginners, starting intermittent fasting with shorter fasting intervals is recommended. The 13-hour fast and the 16:8 fast are both beginner-friendly options.
Are you supposed to fast every day?
Fasting methods can be done daily, such as the 12-hour, 16:8, 18:6, and 20:4 fasts. Fasting periods that last 24 or 36 hours are usually done a few times a week instead of daily. There are many intermittent fasting schedules to try, and each may suit your needs and preferences differently from the next person.
What happens if you fast too often?
Daily fasting is generally safe if you do not have specific medical conditions that require more frequent eating times. A daily 13-hour fast, for instance, should be fine.
However, note that fasting decreases gallbladder movement, which may increase the risk of gallstones when done too often. This is especially true if you’re also a female who is losing weight at a rapid pace (*).
The Bottom Line
Knowing how often you should fast depends on factors such as your eating schedule, fasting experience, and fitness goal.
Those who are just starting with fasting can try fasting frequencies with shorter fasting windows, while more experienced individuals can opt to stretch their fasting periods for as long as 36 hours.
There are many intermittent fasting methods that you can try, all of which are generally safe to do. It helps to consume the right amount of calories for your body type within your window and prioritize nutrient-dense whole foods.
Experiment with each fasting window to see what works for you so you can find out how often you should fast. And last but not least, talk with your healthcare provider if you have a condition and are taking medication.
Shouldn’t that be 11am – 7pm? (not 5pm)?
I was thinking the same thing, Tom. That is what I do.
no because the 11am-5pm window means you are following an 18/6 fasting window regiment.
It’s a typo. The list is identified as examples of the 8 hour fast.
Yeah
Isnt 11-5pm a typo? It should be 11-7pm right?
Hi, thanks for pointing it out. It’s 11am-7pm.
I was wondering how long an intermittent fast should be undertaken. I had been doing it for 6 months, eating 11:30 to 7:30 PM, when I got a flu virus and felt hungry in the mornings so I stopped.
Wondering if at this point I could start again in a few months, or just do it once in a while for 2 weeks? Any thoughts on this? Thanks!
Hi Nancy, there are different types of intermittent fasting. You can check out this article for the type of fasting that would suit you. Hope this can help!
I started keto 2 weeks ago and I am already in ketosis (1.8mmol/L). My body fat 2 weeks ago was 31% and today it is 33% and my muscle mass decreased as well. Question: Does Keto decrease muscle that fast?
Studies have also shown that the low-carb, high-fat ketogenic diet has muscle sparing effects. That means — once you’re fully fat-adapted— your body will prevent itself from breaking down muscle even as you’re burning through fat. You can check more details about muscle building while in keto here: http://perfectketo.com/keto-bodybuilding/
Why does eating a lower amount of carbs reduce hunger pangs?
When you’re on keto, instead of carbs being burned as your source of energy, the fats stored in your body is being used.
Keto is high in fat, protein, and fiber keeping you satisfied and not hungry.
You can check this link to help you know more a about http://perfectketo.com/keto-diet-facts/
I’m 75, went on intermittent fasting cold turkey 20 years ago. I feel great, my weight is down 45 pounds, I sleep better, feel better generally, and will never go back to the SAD way.
If anyone is wanting to fast, grab a copy of Dr. Fung’s book, read it, then start fasting by eating one meal per day.
Fasting promotes cellular housecleaning which the body does not get to do on 3 or 4 meals a day or all-day snacking.
I feel better than at any other time in my life. Don’t be afraid! Just do it!
I am just starting on Keto, I want to try the fasting, I have never done it before. Can you still drink the Base, Collagen, and MTC powder. Does the fasting only refer to solid foods?