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The Many Different Intermittent Fasting Schedules

There are many different intermittent fasting schedules. Read this to find out the differences between each one.
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Summary

We probably all know people who are intermittent fasting, but they all seem to adhere to different fasting/eating schedules. There is no “wrong” intermittent fasting schedule but some could be more challenging than others based on your individual needs and daily activities.

In this article, we define the different types of intermittent fasting and discuss the pros and cons of each one.

Written by
Christine Richardson, PhD
Clinical Project Manager at Becton Dickinson

When it comes to intermittent fasting, it seems like there are so many different fasting/feeding schedules to choose from. 


This may sound confusing especially since other diets don’t operate the same. 


But this is actually what makes intermittent fasting so great - there are many ways women can implement this dietary pattern and still see results.

What Is Intermittent Fasting?


Intermittent fasting is when individuals choose to not consume any calorie-containing foods or beverages for a certain period of time and will switch between periods of fasting and feeding. 


Recently, different types of fasting, specifically intermittent fasting, have become very popular because of its ability to improve one’s health through loss of body fat, decreasing inflammation, reductions in blood pressure, as well as decreasing one’s risk for diseases like type II diabetes, cancer, and more (1, 2, 3, 4). 


Another reason this diet is popular is because it doesn’t require individuals to count their calories or restrict their favorite foods in order to see the benefits.


Different Intermittent Fasting Schedules

A collection of colorful empty plates.


There are many different forms of intermittent fasting. These are different because the amount of time spent fasting and feeding vary. In other words the intermittent fasting schedules are different.


This might sound overwhelming but having a variety of fasting diets to choose from is actually very beneficial because you can pick a form that best accommodates your lifestyle and schedule. 


Below we discuss the different intermittent fasting schedules along with the pros and cons of each so that you can make an informed decision as to which form of fasting that you can be consistent with and will ultimately, be the best for you. 


Alternate Day Fasting

Alternate day fasting is when individuals will alternate between fasting days and feeding days with no restrictions where they eat ad libitum, which is just a fancy way of saying that they eat whatever they want. This is definitely a more extreme form of fasting since the window of fasting is longer than many of the other forms.


On fasting days, individuals consume nothing but water, tea, and maybe some coffee.


Pros/Cons of Alternate Day Fasting

The benefits associated with alternate day fasting include:

  • See health benefits/weight loss quickly
  • Promotes autophagy and ketosis
  • It is easy to get on a routine with alternate day fasting
  • There are no restrictions in terms of eating on your non-fasting days
  • Improves insulin resistance


The cons with alternate day fasting include:

  • A long adjustment time to feeling ok on fasting days
  • May get in the way of social events


Modified Alternate Day Fasting

Calendar with one page for each day.

Modified alternate day fasting is very similar to alternate day fasting except that on the fasting days, individuals will consume a small amount of calories, usually around 500 calories or 25% of their daily calorie needs. 


This is a good form of fasting to use as a “baby step” into alternate day fasting. Going right into alternate day fasting can be hard for some so using this version for a while to ease your way into it is a great strategy.


Pros/Cons of Modified Alternate Day Fasting

The benefits of modified alternate day fasting include:

  • It’s easier than regular alternate day fasting
  • See results quickly
  • Promotes autophagy and ketosis
  • Easy to get on a routine
  • Absolutely no restrictions on eating days
  • Improves insulin resistance


The cons of modified alternate day fasting include:

  • Difficult adjustment period


Whole Day Fasting

Whole day fasting is exactly what it sounds like-fasting for an entire day. 


Individuals who practice whole day fasting will typically pick one day a week (like Sunday) to not consume any calories.


To best make this a habit, try picking the same day every week and make sure to be consistent.


Pros/Cons of Whole Day Fasting

The benefits of whole day fasting include:


The cons of whole day fasting include:

  • May be difficult at first
  • Won’t see benefits as quickly or to same degree as other forms of fasting that are done more frequently/daily


5:2 Fasting

The 5:2 form of intermittent fasting is very similar to whole day fasting. Individuals practicing 5:2 will fast for 2 full days out of the week and eat ad libitum the other 5 days.


Typically, the 2 fasting days are not back-to-back, but there are definitely some people who will go 2 days straight without eating.


Some individuals will opt into eating a small 500 calorie meal on their fasting days.


Pros/Cons of 5:2

The benefits of the 5:2 diet include:


The cons of the 5:2 diet include:

  • May get in the way of social life
  • Can be challenging on fasting days


Time Restricted Feeding

Old-style alarm clock.

Time restricted feeding, also known as time restricted eating, is probably the most popular form of intermittent fasting probably because it is the most flexible intermittent fasting schedule, which makes it the easiest to maintain. 


This dietary pattern is when individuals manipulate their daily timing of calorie consumption by incorporating short-term fasts. To put it simply, to follow this diet, individuals fast for a short amount of time every day by extending the overnight fast.


Most people only fast for about 8 hours a day and with time restricted feeding, individuals fast up to twenty hours a day depending on the eating window they choose. 


OMAD

OMAD stands for one-meal-a-day and is a form of fasting where (you guessed it) individuals only eat one meal a day.


Typically, this meal is eaten at the same time every day and is very calorie-dense. 


We’ve all been taught to be mindful of our caloric intake and most diets dictate that individuals must decrease your caloric intake but keep in mind that your body does NEED food for energy. 


That said, people who incorporate OMAD into their daily habit tend to eat a large meal consisting of all of their caloric needs. This means that their one meal will be about 2000 calories.


Pros/Cons of OMAD

The benefits of OMAD include:


The cons of OMAD include:

  • May be hard to adhere to at first
  • Consuming enough calories may be a challenge
  • May get in the way of social life

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16/8 intermittent fasting

The 16/8 diet is probably the most popular variation of time restricted feeding because the window of fasting is relatively short. For this diet, individuals fast for sixteen hours of the day and eat freely for the remaining eight hours.


The 8-hour period where you eat is up to you and should be chosen wisely based on your schedule and eating preferences. For example, someone who loves eating dinner shouldn’t pick a 7am-3pm eating window. Likewise, someone who loves breakfast shouldn’t pick a 12pm-8pm eating window. This is a recipe for failure.


A variation of the 16/8 diet is the 18/6 diet where individuals fast for 18 hours of the day and eat freely for the other 6 hours. With this form, you simply extend the fast just a few more hours beyond what is required of the 16/8 but still aren’t adhering to one of the more “extreme” versions of intermittent fasting. This is another intermittent fasting schedule that could be easy to maintain.


Pros/Cons of the 16/8 Diet

The benefits associated with the 16/8 diet are:

  • Easiest form of fasting to adhere to
  • Easy to make a habit
  • Won’t get in the way of social life
  • Improves insulin resistance


The cons of the 16/8 Diet are:

  • Health benefits won’t be as quick as other more extreme forms of fasting
  • Consuming enough calories can be a challenge


20/4 intermittent fasting

The 20/4 diet is similar to the 16/8 diet except that individuals fast for 20 hours of the day and eat freely during the remaining four hours. 


This form of time restricted feeding is sometimes confused with OMAD but they are different.  OMAD dictates that individuals eat just one meal a day but with 20/4, you can eat more than one meal over the course of four hours…or you can eat one meal and a snack or two. In short, 20/4 is a little more flexible than OMAD.


Pros/Cons of the 20/4 Diet

The benefits of the 20/4 diet include:


The cons of the 20/4 diet include:

  • May be hard to adhere to at first
  • Consuming enough calories may be a challenge
  • May get in the way of social life


Long-Term Fasting

Calendar in which multiple subsequent days are marked.

Long-term fasting is when people will fast for more than 24 hours. 


There is no strict definition of how long a fast must be in order to qualify as “long-term.” 


For example, sometimes people will fast for 2 days straight while others will embark on a yearly 1-2 week water only fast. Some people enjoy doing a long-term fast to “reset” while others make it a yearly or bi-yearly habit. Others will simply fast for 2 days straight once a month. 


If this is something you decide to try, just keep in mind that no matter how you do it, you did it correctly so long as you aren’t consuming any calorie-containing foods or beverages. 


One thing that we must mention - if you decide to try a long-term fast, be mindful of how you feel, and don’t overdo it your first time. If you feel dizzy, overly lethargic, or cannot attend to normal day-to-day activities, eat something. And always talk to your doctor before trying a long-term fast.


Pros/Cons of Long-Term Fasting 

The benefits of long-term fasting include:

  • People report feeling “refreshed” after
  • New outlook on food
  • Not something that needs to be done daily or weekly
  • Promotes autophagy and ketosis


The cons of long-term fasting include:

  • Can be hard for people to adhere to
  • May have undesired feelings of hunger/sickness, especially during the beginning
  • May not see significant long-term health benefits (more studies are needed)


What is the Best Intermittent Fasting Schedule for Women?

Now that we’ve covered the different forms of fasting, you may be wondering what the best intermittent fasting schedule for women is…and that’s hard to answer.

 

Unfortunately, most research so far on intermittent fasting has used male subjects or males and females without separating the results based on sex. And because male and female physiology can be so different, what is best for men may not necessarily be best for women.

 

Preclinical studies (studies done in animals) have used female animal subjects but a major limitation to this is that the conclusions we see in animals may not apply to humans (5).

 

However, based on a review done by Nair et. al. it appears that fasting can definitely benefit women’s health but it is unknown what the best intermittent fasting schedule is (5).

 

Pick a schedule that you think would work best for you and pay attention to your body and how you feel. If you see an improvement in how you feel and look, then you know you’re on the right track. And if you have any questions or concerns, talk to your doctor.


In Summary

There are many forms of intermittent fasting and all can help you lose weight while improving your health. There is no best intermittent fasting schedule or a “one size fits all” approach to intermittent fasting so evaluate your schedule, habits, and goals before picking a routine.


References:

1. Ganesan K, Habboush Y, Sultan S. Intermittent Fasting: The Choice for a Healthier Lifestyle. Cureus. Cureus, Inc.; 2018 ;10.

2. Paoli A, Tinsley G, Bianco A, Moro T. The influence of meal frequency and timing on health in humans: The role of fasting. Nutrients. MDPI AG; 2019. 

3. Jane L, Atkinson G, Jaime V, Hamilton S, Waller G, Harrison S. Intermittent fasting interventions for the treatment of overweight and obesity in adults aged 18 years and over: a systematic review protocol. JBI database of systematic reviews and implementation reports. JBI Database System Rev Implement Rep; 2015. p. 60–8. 

4. Deligiorgi M V., Liapi C, Trafalis DT. How far are we from prescribing fasting as anticancer medicine? International Journal of Molecular Sciences. MDPI AG; 2020 . p. 1–30.

5.         Nair PMK, Khawale PG. Role of therapeutic fasting in women’s health: An overview. J Midlife Health. Wolters Kluwer -- Medknow Publications; 2016;7:61.


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