What Is Fasting? 11 Different Types Of Fasting, Explained

We'll Break Down What Fasting Is, How It Can Help You, The Risks Involved, And All The Common Types Of Fasting + What They Mean

The practice of fasting for weight loss and health has been around for thousands of years. There are even different types of fasting promoted in the Bible and other religious texts.

But, what exactly are the different types of fasting and intermittent fasting? What are the different types of spiritual fasting? Or what about the best type of fasting for weight loss?

In this article, we will provide a brief definition of what fasting entails and its health effects, before looking at the different types of fasting such as intermittent fasting, religious and spiritual fasting, and fasting for weight loss.

Let’s get started!

A clock on an empty plate with utensils.

What Is Fasting?

Fasting refers to deliberately abstaining from consuming food and caloric beverages for an extended period of time. 

Everyone experiences at least several hours of fasting every day, termed the overnight fast, which occurs during sleep.

But, outside of this, there are many different types of intermittent fasting, spiritual or religious fasting, and health-related fasting.

Depending on your particular goals of fasting, your health status, or your nutritional needs, one type of fasting method may be better or more appropriate for you than another.

A clock made out of a plate and utensils.

What Are The Impacts Of Fasting On Health?

Health Benefits Of Fasting

There is a long list of health benefits from fasting, including:

  • Fat loss1Tinsley, G. M., & La Bounty, P. M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans. Nutrition Reviews73(10), 661–674.
  • Reducing oxidative stress and chronic inflammation2Johnson, J. B., Summer, W., Cutler, R. G., Martin, B., Hyun, D.-H., Dixit, V. D., Pearson, M., Nassar, M., Tellejohan, R., Maudsley, S., Carlson, O., John, S., Laub, D. R., & Mattson, M. P. (2007). Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology and Medicine42(5), 665–674. https://doi.org/10.1016/j.freeradbiomed.2006.12.005
  • Decreasing LDL (“bad”) cholesterol and triglyceride levels3Bhutani, S., Klempel, M. C., Berger, R. A., & Varady, K. A. (2010). Improvements in Coronary Heart Disease Risk Indicators by Alternate-Day Fasting Involve Adipose Tissue Modulations. Obesity18(11), 2152–2159. https://doi.org/10.1038/oby.2010.54
  • Promoting autophagy (cell cleanup) and cellular health4Bagherniya, M., Butler, A. E., Barreto, G. E., & Sahebkar, A. (2018). The effect of fasting or calorie restriction on autophagy induction: A review of the literature. Ageing Research Reviews47, 183–197. https://doi.org/10.1016/j.arr.2018.08.004
  • Boosting the secretion of human growth hormone (HGH)5Horne, B. D., Muhlestein, J. B., & Anderson, J. L. (2015). Health effects of intermittent fasting: hormesis or harm? A systematic review. The American Journal of Clinical Nutrition102(2), 464–470. https://doi.org/10.3945/ajcn.115.109553
  • Improving blood sugar regulation and reducing blood pressure6Barnosky, A. R., Hoddy, K. K., Unterman, T. G., & Varady, K. A. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Translational Research164(4), 302–311. https://doi.org/10.1016/j.trsl.2014.05.013
  • Reducing the risk of disease, including cancer, heart failure, and neurodegenerative diseases7Bartholomew, C. L., Muhlestein, J. B., Anderson, J. L., May, H. T., Knowlton, K. U., Bair, T. L., Le, V. T., Bailey, B. W., & Horne, B. D. (2020). Association of periodic fasting lifestyles with survival and incident major adverse cardiovascular events in patients undergoing cardiac catheterization. European Journal of Preventive Cardiology28(16), 1774–1781. https://doi.org/10.1093/eurjpc/zwaa050Bar-Yosef, T., Damri, O., & Agam, G. (2019). Dual Role of Autophagy in Diseases of the Central Nervous System. Frontiers in Cellular Neuroscience13. https://doi.org/10.3389/fncel.2019.00196

Some individuals also mention that fasting has helped them develop healthier eating patterns.

Health Risks Of Fasting

There are certain types of fasting, particularly extended fasts such as 24-hour water fasts (or more), that may be harmful to those who are pregnant or breast-feeding, have a history of an eating disorder, are underweight according to BMI, have diabetes or another metabolic condition, take certain medications, or have other chronic health conditions.

This is why it is important to speak with your doctor before trying some of the different types of intermittent fasting diets that involve prolonged periods of fasting or other types of spiritual fasting with multiple days of abstaining from eating. 

Moreover, if you are trying to find the best type of fasting for weight loss, again, you should consult your doctor or work with a registered dietitian nutritionist.

They will help you decide if one of the different types of intermittent fasting is best for you, or if a more effective approach to weight loss for you would be a balanced, calorie-controlled diet with exercise.

Intermittent fasting written on a notebook, a clock, a plate and utensils.

What Are the Different Types of Fasting?

Although it would be difficult to make a comprehensive list of every type of fasting, we will try to cover some of the most common types of fasting practiced for weight loss, health, and/or spiritual reasons.

We’ve broken it down into four broad categories of fasting:

  • Intermittent Fasting
  • Religious And Spiritual Fasting
  • Other Types Of Fasting For Weight Loss
  • Modified Fasting Diets

What Type Of Fasting Is Right For Me?

Most types of intermittent fasting or other modified fasting diets have the potential to offer the weight loss and health benefits described above.

However, if you are particularly interested in cell health benefits through autophagy, then you should choose a fast with as close to zero calorie intake as possible.

Many individuals may choose to have some non-fasting days and some fasting days every week, whereas others may do some form of intermittent fasting every day. It depends on what suits the individual best.

Check out our guide on exactly what you can and can’t eat during fasting to learn more.

7 Different Intermittent Fasting Diets Explained

Intermittent fasting is one of the most popular and effective types of fasting for weight loss and health.8Rynders, C. A., Thomas, E. A., Zaman, A., Pan, Z., Catenacci, V. A., & Melanson, E. L. (2019). Effectiveness of Intermittent Fasting and Time-Restricted Feeding Compared to Continuous Energy Restriction for Weight Loss. Nutrients11(10), 2442. https://doi.org/10.3390/nu11102442

Rather than being a specific type of fasting, intermittent fasting is a broad category of fasting such that there are all sorts of iterations and variations on intermittent fasting diet patterns.

Time-Restricted Intermittent Fasting Diets

All of the time-restricted eating types of intermittent fasting involve extending the period of overnight fasting, and then limiting the window of time that you can consume caloric foods and beverages each day.

Different intermittent fasting schedules use this time-restricted fasting approach.

With any of these time-restricted feeding types of intermittent fasting, you have complete flexibility in terms of how you schedule your fasting and eating windows.

For example, with the 16/8 intermittent fasting diet, you have a 16-hour fast and an 8-hour eating window.

Thus, you might use something around the 10 AM to 6 PM, 11 AM to 7 PM, or noon to 8 PM range for your eating window.

However, it is entirely up to you and certainly doesn’t have to be done right on the hour, as long as you are sticking with the 16-hour fast and 8-hour eating blocks of time.

A blue clock and a salad.

Let’s break down some of the most common time-restricted intermittent fasting schedules:

12/12 Intermittent Fasting Diet

A beginner-friendly type of intermittent fasting diet is the 12/12 intermittent fasting schedule.

This entails splitting the 24-hour day into two equal parts: a 12-hour fast and a 12-hour eating window.

You might fast from 7:00 PM to 7:00 AM, 8:00 AM to 8:00 PM, or something similar.

14/10 Intermittent Fasting Diet

The next easiest type of intermittent fasting diet is 14/10 intermittent fasting, which involves a 14-hour fast and a 10-hour eating window.

16/8 Intermittent Fasting Diet

The 16/8 intermittent fasting diet schedule is probably the most popular type of intermittent fasting pattern. 

It involves fasting for 16 hours per day with a permissible eating window that lasts eight hours.

This might look something like beginning your overnight fast after dinner at 6 PM and then fasting through the entire night until the next day at 10:00 AM, when you would break your fast with your first meal. 

A clock on an empty plate with utensils.

18/6 Intermittent Fasting Diet

18/6 intermittent fasting involves fasting for 18 hours per day and confining all of your eating to just six hours.

This is a doable progression for those who have tried 16/8 intermittent fasting and want to limit eating hours even more.

A common way to split this up is to fast from 6:00 PM to noon the next day or 7:00 PM to 1:00 PM.

20/4 Intermittent Fasting (Warrior Diet)

The 20/4 intermittent fasting diet is also called the “Warrior Diet,” and it involves a 20-hour fast and a four-hour eating window, which can be logistically, physically, and mentally challenging because it is very difficult to go up for 20 hours without eating.

With this type of intermittent fasting, people often begin the overnight fast at 6 PM and continue to fast all the way until 2 PM the next day or something similar.

A clock next to an empty plate with utensils.

Other Types of Intermittent Fasting Diets

Alternate Day Fasting

Alternate-day fasting, also called ADF fasting, for short, is an approach to intermittent fasting diets that uses a fasting schedule for the week as a whole scale rather than each individual day.

This type of intermittent fasting diet involves fasting every other day and then consuming what you want to eat, and when you want to eat it on the days you are not fasting.

Essentially, you do a full 24-hour water fast every other day and eat normally at liberty on alternate days. 

5:2 Intermittent Fasting Diet

The 5:2 diet, also known as the Fast Diet, the 5&2 diet, or the 5/2 diet, is a specific dietary approach to an intermittent fasting diet. 

This type of fasting diet is so named because it involves following your regular diet and caloric intake for five days of the week and then severely restricting calories (to 500–600 per day) the other two days of the week.

Along the lines of alternate-day fasting, the 5:2 diet involves restricting the total number of calories you eat during two days of the week. Like other types of intermittent fasting, how you consume these calories—your food choices—is not dictated by the diet.

A clock on an empty plate with utensils.

OMAD

OMAD is a type of fasting that entails eating only one meal a day.

This is essentially a 23-hour fast.

You might have your one meal a day every night at 5 PM and then fast until the next day at 5 PM, or you have the flexibility to choose when you are going to eat your one meal a day on OMAD as long as you are only eating one meal on every calendar day.

Religious And Spiritual Fasting Explained

Different types of fasting exist in some form in all major religions including Buddhism, Hinduism, Taoism, Christianity, Islam, Judaism, Jainism, and Sikhism.

Fasting periods in religions can range from one day to a month or more.

There are also several different types of fasting related to non-religious spirituality and alternative medicine.

In religion and spirituality, fasting is often tied to concepts of purification, self-sacrifice, abstinence, longevity, ritual, and closeness to God.

Types of Fasting In the Bible

The Bible refers to many different types of fasting, and there is no clear answer as to the number of types of fasting in the Bible.9What are the different types of fasting? (n.d.). GotQuestions.org. Retrieved December 21, 2023, from https://www.gotquestions.org/types-of-fasting.html

This is because different sources categorize Biblical fasts in different ways—either in broad sweeping categories of fasting in the Bible or as more specific examples.

The general types of fasting in the Bible are a regular fast (no food), an absolute fast (no food or drink), and a partial fast (also called a Daniel fast; fasting from certain foods).10Luke 4:2 ESV – for forty days, being tempted by…. (n.d.). Biblia. Retrieved December 21, 2023, from https://biblia.com/bible/esv/luke/4/2Esther 4:16 ESV – “Go, gather all the Jews to be…. (n.d.). Biblia. Retrieved December 21, 2023, from https://biblia.com/bible/esv/esther/4/16Daniel 10:2–3 ESV – In those days I, Daniel, was…. (n.d.). Biblia. Retrieved December 21, 2023, from https://biblia.com/bible/esv/daniel/10/2-3

A clock with the word fasting in front of it.

Other Types of Fasting for Weight Loss Explained

Prolonged Water Fasting

Aside from intermittent fasting, other types of fasting are even more extreme and may be performed for weight loss, health, or spiritual reasons.

Water fasting is complete fasting in that you can only have water and non-caloric beverages, just as with the fasting windows during any type of intermittent fasting diet.

However, some people might perform an extended fast such as a 24-hour water fast, a 48-hour water fast, or even a 5-day water fast or more.

Modified Fasting Diets Explained

In addition to strict fasting, or water fasting, in which you abstain from consuming any foods or caloric beverages, some other types of fasting are more lax.

Although these “modified types of fasting“ are not technically true fasting, they may still be grouped under the umbrella of ‘types of fasting’ and can still offer the health benefits of fasting with less hunger and fatigue, as an individual is still consuming nutrients during the fast.11Zajac, I., Herreen, D., Hunkin, H., James-Martin, G., Doyen, M., Kakoschke, N., & Brindal, E. (2020). Modified Fasting Compared to True Fasting Improves Blood Glucose Levels and Subjective Experiences of Hunger, Food Cravings and Mental Fatigue, But Not Cognitive Function: Results of an Acute Randomised Cross-Over Trial. Nutrients13(1), 65. https://doi.org/10.3390/nu13010065

Most of these modified fasting protocols can also be considered “cleanses“ or “extreme diets“ for rapid weight loss and are sometimes referred to as “dirty fasting” or “partial fasting.”

A clock on an empty plate with utensils.

Essentially, the dieter will consume some amount of food or caloric beverage during the partial fast or dirty fasting diet.

Examples include the watermelon fasting diet, juice cleanses that focus primarily on beverages made with lemon juice, cayenne pepper, and maple syrup, drinking Bulletproof coffee (coffee with cream and MCT oil), or a liquid diet, without the consumption of solid food.

An example of this type of fast in the Bible can be seen in the Book of Daniel, where followers in captivity ate only fruit and vegetables and drank water for ten days to honor God.

“Please test your servants for ten days, and let us be given some vegetables to eat and water to drink.” (Daniel 1:12 NASB)12Daniel 1:12 KJV – – Bible Gateway. (n.d.). Www.biblegateway.com. Retrieved December 21, 2023, from https://www.biblegateway.com/passage/?search=Daniel+1%3A12&version=KJV

Overall, choosing the best type of fasting is a matter of considering the pros and cons of the type of fasting diet, your current health status, and your health and weight loss goals and needs.

Other FAQs

How Much Weight Can I Lose From Intermittent Fasting?

A review of 40 studies into intermittent fasting for weight loss found a typical weight loss of 7 to 11 pounds over ten weeks.13Seimon, R. V., Roekenes, J. A., Zibellini, J., Zhu, B., Gibson, A. A., Hills, A. P., Wood, R. E., King, N. A., Byrne, N. M., & Sainsbury, A. (2015). Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials. Molecular and Cellular Endocrinology418, 153–172. https://doi.org/10.1016/j.mce.2015.09.014

How Many Days Can Someone Do Intermittent Fasting?

If an individual can consume enough calories and maintain good health, then it is possible to fast every day.

However, continual weight loss through fasting is not going to be sustainable forever, and you should pay close attention to any side effects.

Some individuals may choose to fast for short-term periods, before returning to a normal diet.

As mentioned previously, extended periods of calorie restriction through fasting can be particularly dangerous for individuals who are pregnant or breast-feeding, have a history of an eating disorder, are underweight according to BMI, have diabetes or another metabolic condition, take certain medications, or have other chronic health conditions.

Before fasting for an extended period you should speak to your doctor.

Conclusions

Intermittent fasting diets with shorter fasts are easier logistically and physically and more similar to how people normally schedule their food intake but may not offer all of the potential benefits of fasting for longer durations.14Gill, S., & Panda, S. (2015). A Smartphone App Reveals Erratic Diurnal Eating Patterns in Humans that Can Be Modulated for Health Benefits. Cell Metabolism22(5), 789–798. https://doi.org/10.1016/j.cmet.2015.09.005Kerndt, P. R., Naughton, J. L., Driscoll, C. E., & Loxterkamp, D. A. (1982). Fasting: the history, pathophysiology and complications. The Western Journal of Medicine137(5), 379–399. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1274154/

For example, autophagy and significant increases in growth hormone can take close to 48 hours to really take effect, and even getting into ketosis generally takes 18-24 hours, depending on factors such as your body size, your diet composition, if you are an endurance-trained athlete, and if you have been performing exercise while fasting.15de Cabo, R., & Mattson, M. P. (2019). Effects of Intermittent Fasting on Health, Aging, and Disease. New England Journal of Medicine381(26), 2541–2551. https://doi.org/10.1056/nejmra1905136Weltan, S. M., Bosch, A. N., Dennis, S. C., & Noakes, T. D. (1998). Influence of muscle glycogen content on metabolic regulation. American Journal of Physiology-Endocrinology and Metabolism274(1), E72–E82. https://doi.org/10.1152/ajpendo.1998.274.1.e72

It is highly recommended that you speak with your healthcare provider before beginning any of these types of fasting, particularly more aggressive intermittent fasting diets or prolonged fasting.

If you are intrigued by the potential fasting benefits, you can read more about the benefits of fasting here.

Two empty plates and utensils.

References

  • 1
    Tinsley, G. M., & La Bounty, P. M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans. Nutrition Reviews73(10), 661–674.
  • 2
    Johnson, J. B., Summer, W., Cutler, R. G., Martin, B., Hyun, D.-H., Dixit, V. D., Pearson, M., Nassar, M., Tellejohan, R., Maudsley, S., Carlson, O., John, S., Laub, D. R., & Mattson, M. P. (2007). Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology and Medicine42(5), 665–674. https://doi.org/10.1016/j.freeradbiomed.2006.12.005
  • 3
    Bhutani, S., Klempel, M. C., Berger, R. A., & Varady, K. A. (2010). Improvements in Coronary Heart Disease Risk Indicators by Alternate-Day Fasting Involve Adipose Tissue Modulations. Obesity18(11), 2152–2159. https://doi.org/10.1038/oby.2010.54
  • 4
    Bagherniya, M., Butler, A. E., Barreto, G. E., & Sahebkar, A. (2018). The effect of fasting or calorie restriction on autophagy induction: A review of the literature. Ageing Research Reviews47, 183–197. https://doi.org/10.1016/j.arr.2018.08.004
  • 5
    Horne, B. D., Muhlestein, J. B., & Anderson, J. L. (2015). Health effects of intermittent fasting: hormesis or harm? A systematic review. The American Journal of Clinical Nutrition102(2), 464–470. https://doi.org/10.3945/ajcn.115.109553
  • 6
    Barnosky, A. R., Hoddy, K. K., Unterman, T. G., & Varady, K. A. (2014). Intermittent fasting vs daily calorie restriction for type 2 diabetes prevention: a review of human findings. Translational Research164(4), 302–311. https://doi.org/10.1016/j.trsl.2014.05.013
  • 7
    Bartholomew, C. L., Muhlestein, J. B., Anderson, J. L., May, H. T., Knowlton, K. U., Bair, T. L., Le, V. T., Bailey, B. W., & Horne, B. D. (2020). Association of periodic fasting lifestyles with survival and incident major adverse cardiovascular events in patients undergoing cardiac catheterization. European Journal of Preventive Cardiology28(16), 1774–1781. https://doi.org/10.1093/eurjpc/zwaa050Bar-Yosef, T., Damri, O., & Agam, G. (2019). Dual Role of Autophagy in Diseases of the Central Nervous System. Frontiers in Cellular Neuroscience13. https://doi.org/10.3389/fncel.2019.00196
  • 8
    Rynders, C. A., Thomas, E. A., Zaman, A., Pan, Z., Catenacci, V. A., & Melanson, E. L. (2019). Effectiveness of Intermittent Fasting and Time-Restricted Feeding Compared to Continuous Energy Restriction for Weight Loss. Nutrients11(10), 2442. https://doi.org/10.3390/nu11102442
  • 9
    What are the different types of fasting? (n.d.). GotQuestions.org. Retrieved December 21, 2023, from https://www.gotquestions.org/types-of-fasting.html
  • 10
    Luke 4:2 ESV – for forty days, being tempted by…. (n.d.). Biblia. Retrieved December 21, 2023, from https://biblia.com/bible/esv/luke/4/2Esther 4:16 ESV – “Go, gather all the Jews to be…. (n.d.). Biblia. Retrieved December 21, 2023, from https://biblia.com/bible/esv/esther/4/16Daniel 10:2–3 ESV – In those days I, Daniel, was…. (n.d.). Biblia. Retrieved December 21, 2023, from https://biblia.com/bible/esv/daniel/10/2-3
  • 11
    Zajac, I., Herreen, D., Hunkin, H., James-Martin, G., Doyen, M., Kakoschke, N., & Brindal, E. (2020). Modified Fasting Compared to True Fasting Improves Blood Glucose Levels and Subjective Experiences of Hunger, Food Cravings and Mental Fatigue, But Not Cognitive Function: Results of an Acute Randomised Cross-Over Trial. Nutrients13(1), 65. https://doi.org/10.3390/nu13010065
  • 12
    Daniel 1:12 KJV – – Bible Gateway. (n.d.). Www.biblegateway.com. Retrieved December 21, 2023, from https://www.biblegateway.com/passage/?search=Daniel+1%3A12&version=KJV
  • 13
    Seimon, R. V., Roekenes, J. A., Zibellini, J., Zhu, B., Gibson, A. A., Hills, A. P., Wood, R. E., King, N. A., Byrne, N. M., & Sainsbury, A. (2015). Do intermittent diets provide physiological benefits over continuous diets for weight loss? A systematic review of clinical trials. Molecular and Cellular Endocrinology418, 153–172. https://doi.org/10.1016/j.mce.2015.09.014
  • 14
    Gill, S., & Panda, S. (2015). A Smartphone App Reveals Erratic Diurnal Eating Patterns in Humans that Can Be Modulated for Health Benefits. Cell Metabolism22(5), 789–798. https://doi.org/10.1016/j.cmet.2015.09.005Kerndt, P. R., Naughton, J. L., Driscoll, C. E., & Loxterkamp, D. A. (1982). Fasting: the history, pathophysiology and complications. The Western Journal of Medicine137(5), 379–399. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1274154/
  • 15
    de Cabo, R., & Mattson, M. P. (2019). Effects of Intermittent Fasting on Health, Aging, and Disease. New England Journal of Medicine381(26), 2541–2551. https://doi.org/10.1056/nejmra1905136Weltan, S. M., Bosch, A. N., Dennis, S. C., & Noakes, T. D. (1998). Influence of muscle glycogen content on metabolic regulation. American Journal of Physiology-Endocrinology and Metabolism274(1), E72–E82. https://doi.org/10.1152/ajpendo.1998.274.1.e72
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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