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The 8 different methods of intermittent fasting

There are many different intermittent fasting methods, which mainly differ in fasting duration. We explain the most popular methods.
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Summary

There are multiple intermittent fasting methods, which mainly differ in fasting duration: from a 12-hour overnight fast to a whole-day fast. Methods with a short fasting period are well-suited for beginners. Longer fasting periods provide more benefits and are recommended for experienced fasters.

Written by
Sarah Neidler, PhD
Freelance Science and Medical Writer

When you hear intermittent fasting, 16/8 fasting probably comes to mind.


But intermittent fasting is a broad term that includes many different fasting schedules.


The duration of the fast is the main differentiator: Some methods simply extend the overnight fast by a few hours, while with others, you abstain from food for a whole day.


Let’s have a closer look at different intermittent fasting methods.


1. 12-hour or overnight fasting

12-hour fasting is the absolute beginner version. You fast for 12 hours every day, and it includes your nightly fast. So you simply fast for a short period before getting to bed and after waking up.


You typically eat three meals: breakfast, lunch, and dinner. This sounds more like a normal eating schedule and less like fasting. The difference is that you abstain from snacking, which would shorten your fasting time. Let’s say you finish dinner by 7 pm–that’s when your fast starts. If you were to keep snacking after dinner, this would shorten your fasting period by a few hours.


You may think that this small difference does not have a big effect–but you’d be wrong. In a study  of diabetic patients, findings showed that eating three meals per day without snacking significantly decreased their weight and lowered blood sugar. At the same time, the insulin dose could be lowered (1).


How is this possible?

Every time you eat something, your blood sugar and insulin rises and takes a while to go back to normal. When you constantly snack, blood sugar, and insulin have hardly time to come down in-between snacks.


With only three meals, blood sugar and insulin rise only three times, and the levels are in the normal range for most of the day. For this reason, sticking to three meals without snacking already helps to lower insulin and improve insulin resistance (the underlying cause of type 2 diabetes). And because insulin does not only lower blood sugar but is also a fat-storage hormone, keeping insulin low also helps to lose weight. 


So, even if you don’t have diabetes, constant snacking increases your diabetes risk, so avoiding it decreases your chances and improves overall health.


There is another way to practice 12-hour fasting–eating only two meals: breakfast and dinner. This way, you have two long fasting periods per day. This schedule suits many people who like to eat breakfast in the morning and want to enjoy a social dinner with family or friends but don’t have much time for lunch at work.


Recommended for:

  • Beginners
  • People who don’t have much weight to lose but would like to experience the health benefits of intermittent fasting

Main benefits:

  • Regular eating times with breakfast, lunch and dinner
  • Improves overall health and decreases the risk of chronic conditions, such as diabetes

2. 14/10 fasting

14/10 intermittent fasting is another beginner-friendly method that you can immediately implement without prior fasting experience. You fast for 14 hours and eat within a ten-hour period.


14/10 is popular among women who struggle with longer fasting periods, because it is easy but has similar benefits as the famous 16/8 method.


You can eat two or three meals during your eating window. If you eat three meals, you have to move them a bit closer together. With two meals, you have quite a long break in between.


Recommended for:

  • Beginners
  • Women who struggle with longer fasting periods


Main benefits:

  • Easy to implement
  • Facilitates weight loss


3. 16/8-fasting 

Old-style alarm clock.

16/8 fasting is the most popular intermittent fasting method. It is a bit more advanced than the first two versions, but still very beginner-friendly. You eat within an eight-hour period every day and fast for 16 hours. 


Most people eat two meals during this period: Either breakfast and lunch or lunch and dinner. It is also possible to eat three meals; you just have to shorten the time between meals to stay within an eight-hour window. 


Most people can easily adapt to 16/8 within a short time, and they can lose weight without feeling hungry. What’s nice about this form is that even though it’s relatively simple to do, you can still expect to see results. Studies have shown that the 16/8 diet can help individuals lose weight, improve insulin resistance, and decrease inflammation, while maintaining muscle mass (2, 3).


After 16 hours of fasting, autophagy is expected to start. Autophagy is a vital recycling process that is responsible for many of the health benefits of intermittent fasting. Longer fasting times are more potent in promoting autophagy, but 16-18 hours are already sufficient to start this process.


You can learn more about this in our article about fasting and autophagy.


A potential con to this method is that you may not see results as quickly as someone who is on a more restrictive fasting diet, like alternate day fasting. You are also probably not unlocking all of the anti-aging and longevity potential that fasting can offer you. 


But this is a great form if you’re new to fasting or enjoy going out to eat with friends and family regularly!


Once you get used to 16/8 fasting and feel that you could easily fast for longer, you can also switch to 18/6 intermittent fasting. This is a popular variation of 16/8 fasting and simply means that your fasting time is 2 longer than with 16/8.


Recommended for:

  • Beginners and people with some fasting experience
  • People of normal weight or slightly overweight 


Main benefits:

  • Facilitates weight loss
  • Powerful method to reduce insulin resistance
  • Promotes autophagy



4. Warrior diet or OMAD

Warrior in a suit of armor.

OMAD stands for One-Meal-A-Day. You eat only once per day, as the name implies. Most people have dinner as their only meal because it fits their schedule best. This way, you achieve a daily fasting time of around 23 hours. 


The warrior diet is a variation of OMAD and was popularized by the fitness expert Ori Hofmekler: you eat small amounts of fruits, nuts, and vegetables during the day and have one big meal in the evening. 


OMAD is quite an advanced version of intermittent fasting. Still, some people who are not hungry in the morning and have not much appetite at lunch find it quite easy.


In order to successfully do OMAD, pick a time that you want to eat daily and eat all of your daily caloric needs at that time. And yes, this should be a very calorie-dense meal. If you decide to try OMAD, you shouldn’t be eating 500 calories a day - you should be eating 1500-2000+ depending on your age, sex, height, and physical activity level. 


Eating too few calories long-term has been shown to be harmful to your health so this is something you should keep in mind when trying OMAD. It may be difficult to eat so much at first, and that’s fine, but after a couple weeks, your body should adapt and eating a calorie-dense meal should become much easier. If you still find eating this much impossible, this may not be the best diet for you.


With only one meal a day, insulin levels are low for the major part of the day. For this reason, OMAD is a powerful weight-loss method. Moreover, this long fasting time puts the body in a state of ketosis.  During ketosis, fat is turned into ketone bodies, which present an additional fuel source. Ketosis is very powerful for weight loss because it enables access to fat storage.  


A con to this strategy is that going the whole day without eating may be very difficult for some people. If you try this and are really struggling, try easing into it by extending your fast gradually until you can go through most of the day without eating. Practice makes perfect.


Recommended for:

  • People with intermittent fasting experience
  • People with a busy schedule who don’t have time to eat during the day


Main benefits:

  • Promotes autophagy
  • Enables ketosis
  • Facilitates weight loss


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5. Eat Stop Eat 

The Eat Stop Eat method is similar to OMAD: You fast for 24 hours, from one meal to the same meal the next day. For example, from lunch on one day until lunch the next day. 


The main difference compared to OMAD is that you do it only once or twice a week instead of every day. 


A con to this diet is that because it’s only once or twice a week, you might simply wake up on your fasting day and start eating because you forgot…try setting a reminder on your phone or on a post-it to remind you on your designated fasting day until it becomes a strict habit of yours. It might be a good strategy to commit to the same day(s) each week, like Sunday and Thursday; this will help instill the habit.


Another con is that because this isn’t happening every day, it may take a little bit longer for you to notice any results when compared to alternate day fasting or OMAD. But don’t let that discourage you! Your journey is yours alone and any progress is great success ☺ 


Recommended for:

  • People with intermittent fasting experience
  • People who don’t want to fast every day


Main benefits:

  • Promotes autophagy
  • Enables ketosis



6. Alternate-Day-Fasting (ADF)

ADF stands for alternate-day fasting. As the name implies, you eat every other day. With ADF, you achieve a fasting time of around 36 hours: From dinner on one day until breakfast on the day after the next. 


Alternate day fasting is probably one of the most effective forms of intermittent fasting because the fasting period is so long. Studies have shown time and time again how effective this method can be with helping individuals lose weight, control their blood sugar levels, decrease their blood pressure, and more (4, 5).

Studies have also shown that alternate day fasting is very effective at increasing autophagy, minimizing signs of aging, and even increasing your lifespan…some animal studies show an increase in lifespan up to 80% (6, 7).


While alternate day fasting may sound like an easy habit to try, not eating for an entire day can be a lot harder than it sounds. Some people, especially individuals who currently eat for 15+ hours a day, may really struggle when first trying this method. 


ADF is not for everyone, and you don’t have to fast for so long to experience the benefits of intermittent fasting. If you would like to try it, please consult your GP beforehand.


Modified Alternate Day Fasting

Modified alternate day fasting is very similar to alternate day fasting except that individuals eat an approximate 500 calorie meal on their fasting days. While you can definitely see results using this strategy, you shouldn’t expect to reap all of the benefits associated with true alternate day fasting. 


This modified strategy, however, could be a great strategy for individuals who want to try alternate day fasting but are struggling to get through the entire day. Do this form for a while and then try graduating to a full day’s fast.


Recommended for:

  • People who have considerable fasting experience
  • People who have a lot of weight to lose
  • People who want to reverse diabetes (only after consultation with their GP)


Main benefits:

  • Powerful method to lose a lot of weight within a short time
  • Maximizes autophagy
  • Enables deep ketosis
  • Reduces insulin resistance



7. 5:2 fasting

5:2 fasting is similar to ADF, but you fast only for two (non-consecutive) days per week and eat normally on the five remaining days. 


You typically eat 500 - 600 kcal on the fasting days, but you can also completely abstain from food. 


Similar to ADF, 5:2 is a very advanced intermittent fasting method. If you would like to try it, please consult your GP beforehand.


Recommended for:

  • People with fasting experience
  • People who don’t want to fast every day


Main benefits:

  • Reduces insulin resistance
  • Promotes autophagy
  • Enables ketosis
  • Facilitates weight loss


8. Intuitive intermittent fasting or spontaneous meal skipping

Man with a heart and a brain.

Many people enjoy intermittent fasting but don’t want to adhere to a set eating schedule. That’s totally fine! After all, the most important thing is to have regular eating breaks and not to have them at the same time each day. 


A more intuitive approach to intermittent fasting is common among people who have practiced intermittent fasting for a while and got used to this way of eating.


The idea behind intuitive intermittent fasting is to eat only when you are really hungry, and to eat until you are full. When it’s time to eat, but you don’t feel hungry, you spontaneously skip a meal. 


When you start experimenting with intermittent fasting, the intuitive version also helps you find the intermittent fasting method that suits you best. You can test how long you can go without food without feeling cranky and find out at what times of the day fasting is easiest. 


Miscellaneous Forms

Four clocks showing different times.

While the intermittent fasting methods we mentioned above are probably the most commonly used, don’t think you can’t make up your own version.


For example, you could fast for 13 hours per day or try a 20/4 version where you fast for 20 hours of the day and eat for the remaining 4 hours.


You can also mix and match. Some individuals will implement the 16/8 diet 6 days of the week and then fast completely on the remaining day. 


The nice thing about intermittent fasting is that there is some wiggle room where you can play around with the eating timeframe. 



Bottom line

There are many different methods of intermittent fasting. One challenge at the beginning is to find out which method suits you best.


If you force yourself to follow a fasting schedule that is not a good fit for you, you will probably decide that intermittent fasting isn’t for you. On the other hand, if you find a method that perfectly aligns with your needs and schedule, it will soon become second nature without having to watch the clock. 


You learn more about this in our article about choosing the right fasting window.


References:

1. Jakubowicz D, Landau Z, Tsameret S, et al. Reduction in Glycated Hemoglobin and Daily Insulin Dose Alongside Circadian Clock Upregulation in Patients With Type 2 Diabetes Consuming a Three-Meal Diet: A Randomized Clinical Trial. Diabetes Care. Dec 2019;42(12):2171-2180. doi:10.2337/dc19-1142

2. Moro T, Tinsley G, Bianco A, Marcolin G, Pacelli QF, Battaglia G, Palma A, Gentil P, Neri M, Paoli A. Effects of eight weeks of time-restricted feeding (16/8) on basal metabolism, maximal strength, body composition, inflammation, and cardiovascular risk factors in resistance-trained males. J Transl Med. 2016;14:290. 

3. Stratton MT, Tinsley GM, Alesi MG, Hester GM, Olmos AA, Serafini PR, Modjeski AS, Mangine GT, King K, Savage SN, et al. Four weeks of time-restricted feeding combined with resistance training does not differentially influence measures of body composition, muscle performance, resting energy expenditure, and blood biomarkers. Nutrients. 2020;12. 

4. Trepanowski JF, Kroeger CM, Barnosky A, Klempel MC, Bhutani S, Hoddy KK, Gabel K, Freels S, Rigdon J, Rood J, et al. Effect of alternate-day fasting on weight loss, weight maintenance, and cardioprotection among metabolically healthy obese adults: A randomized clinical trial. JAMA Intern Med. American Medical Association; 2017;177:930–8. 

5. Eshghinia S, Mohammadzadeh F. The effects of modified alternate-day fasting diet on weight loss and CAD risk factors in overweight and obese women. J Diabetes Metab Disord. Springer; 2013;12:4. 

6. Cui Y, Cai T, Zhou Z, Mu Y, Lu Y, Gao Z, Wu J, Zhang Y. Health Effects of Alternate-Day Fasting in Adults: A Systematic Review and Meta-Analysis. Frontiers in Nutrition. 2020; p. 586036. 

7. Goodrick CL, Ingram DK, Reynolds MA, Freeman JR, Cider NL. Effects on intermittent feeding upon growth and life span in rats. Gerontology. 1982;28:233–41. 


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