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type of intermittent fasting

Which Type of Intermittent Fasting Should You Try?

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(Last Updated On: January 19, 2022)
type of intermittent fasting, types of intermittent fasting
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If you’re wondering the best type of intermittent fasting for you, there are a few key options that tend to be popular. We’ll talk more about the benefits of intermittent fasting and then provide an overview about choosing the type of intermittent fasting that might work for you.[1]

What Is Intermittent Fasting?

Intermittent fasting or IF is one of the most popular trends in the health and wellness world right now. While it may be trending, it’s not a new concept.

  • The idea of restricting your food intake based on when you eat dates back to ancestral times.
  • Our ancestors didn’t always have food because they were hunters and gatherers.
  • There would be periods where they ate nothing and other times when they feasted.
  •  The idea of IF is that our bodies are designed explicitly for this eating pattern, rather than three or four meals a day.

As research continues on fasting, we’re learning that it has potentially powerful benefits for physical health, weight loss, and mental and brain health.[2]

The idea of intermittent fasting is that you follow an eating pattern where you cycle between eating and fasting.

  •  You don’t have to follow a particular diet regarding your calories or what you eat. Instead, you’re eating based on time periods. The restriction relies on when you eat.[3]
  • Our bodies evolved to function without eating for much longer time periods than many of us realize.
  • Fasting is also practiced in the world’s most popular religions, including Christianity, Islam, and Judaism.

How Does Fasting Work?

When you fast, you choose periods where you won’t eat and periods where you will.

  • When you go for an extended period without eating, your body goes through its stores of sugar and starts burning fat.
  • This process is sometimes called metabolic switching.
  • The idea is very much a contrast from how we usually think about eating. We often follow eating patterns where we’re eating throughout our hours when we’re awake.
  • When you’re continuously feeding your body three meals a day and snacks, you’re using those calories for energy each time you eat, and you’re not burning your stored fat.
  • When you practice fasting, you’re extending the period where your body is burning through calories you had during your last meal so that you then begin to burn fat.

What Are the Benefits of Fasting?

We’re starting to get a clearer idea of how beneficial fasting is for our mental and physical well-being.

  • According to research, when your body goes through an intermittent fasting period, you burn fat.
  • However, there are also changes in your metabolism that affect your brain.
  • In one study published in the New England Journal of Medicine, researchers found benefits of fasting for periods of time can include a leaner body, sharper mind, and longer life.

Many things happen during intermittent fasting that can protect your organs against chronic diseases, including heart disease, inflammatory bowel disease, certain types of cancer, type 2 diabetes, and neurodegenerative diseases.

Below, we talk more about some of the benefits of fasting.

Weight Loss

Losing weight is probably one of the most common reasons people intermittent fast. There are a few ways fasting can help you lose weight.[4]

  • First, you’re skipping meals so you can reduce your calorie intake.
  • You have to be careful that you’re not overdoing it during your feeding periods.
  • In one study, intermittent fasting led to a 4-7% reduction in waist circumference, meaning a loss of belly fat stores. 
  • There are also weight loss benefits because of how fasting impacts your hormones. Your body fat is how your body stores energy. When you’re not consuming calories, your body makes changes to promote accessibility of stored energy.
  • When you eat, your insulin levels go up. When you fast, they go down significantly. Lower insulin levels promote fat burning.[5]
  • Your nervous system also sends norepinephrine to your fat cells so that they then break down your body fat into fatty acids burned for energy.[6]
  • Human growth hormone is changed during fasting too. Levels may increase as much as five-fold when you fast.

Blood Sugar Control and Reduced Insulin Resistance

We briefly discussed this, but studies show fasting can improve blood sugar control.

  • In a study of 10 people with type 2 diabetes, short-term fasting significantly lowered blood sugar levels.
  • Another review found there were benefits of alternate-day fasting and intermittent fasting.
  • When insulin resistance goes down, your body becomes more sensitive to insulin.
  • That increase in insulin sensitivity means your body can move glucose from your bloodstream to your cells more efficiently.
  • This effect then keeps your blood sugar levels steady, helping you avoid spikes and crashes.

Lower Inflammation

Chronic inflammation is something that may be the root of many of the most serious illnesses we deal with in our modern lives, including cancer, rheumatoid arthritis, and heart disease.

In studies, fasting helps decrease inflammation levels and promote improvements in health.

For example, in a study of 50 healthy adults, intermittent fasting for a month led to significant decreases in inflammatory markers.

Cardiovascular Health

Heart disease is one of the leading causes of death for people worldwide. When you change your diet and lifestyle, you can reduce your risk of developing heart disease. Fasting may be beneficial for heart health.[7]

For example, participants had lower LDL cholesterol levels in one study of eight weeks of alternate-day fasting. There were also significant reductions in blood triglycerides.[8]

An intermittent fasting plan can lower your blood pressure and generally improve your metabolic health in significant ways. 

Brain Health and Function

Studies currently limited to animals have found fasting can affect brain health in powerful ways.

  • For example, a study in mice found intermittent fasting for 11 months improved brain structure and function.
  • Other animal studies show fasting could protect the brain’s health and promote the generation of nerve cells, improving cognitive function.
  • Since fasting is also thought to reduce inflammation, it may help prevent neurodegenerative disorders.
  • Fasting could protect against disorders like Alzheimer’s and Parkinson’s or improve outcomes.[9]

Boosts Metabolism

There’s some research indicating short-term periods of fasting can boost your metabolism. When you practice short-term fasts, it can increase the levels of the neurotransmitter norepinephrine, improving weight loss.

Fasting may help you continue to have a boosted metabolism even on your non-fasting days if you do alternate-day. 

Slows Aging and Extends Lifespan

Animal studies currently indicate that fasting can help extend lifespan and reduce signs of aging. For example, in a study of rats fasting every other day, there was a delayed rate of aging. The fasting rats lived 83% longer than the ones who didn’t.

Regularly engaging in caloric restriction through fasting can reduce the risk of so many types of chronic disease associated with aging.[10]

Fasting Triggers Regeneration of The Immune System

In my opinion, one of perhaps the most exciting benefits of fasting is that researchers found it may help your body remove old cells and create a new immune system.

  • The stem cells may be shifted from dormant to a state of self-renewal after periods of fasting.
  • In a study of mice and humans in patients receiving chemo, long periods of not eating lowered white blood cell counts.
  • Then, in mice, fasting cycles flipped a switch of regeneration, changing signaling pathways for hematopoietic stem cells. Those stems cells are responsible for generating blood and immune systems.[11]

This research could help us learn more about healthy aging because declines in the immune system can increase susceptibility to disease as we age.

There could also be implications for dealing with many immune system deficiencies, including autoimmune disorders.[12]

Which of the Fasting Methods Should You Try?

While the benefits are immense, there are different types of intermittent fasting.

Below, we go over some of the details of the most popular types of intermittent fasting so you can figure out which one might be ideal for you.

Type of Fasting Method

Key Points

Pros

Cons

16/8

Fast for 16 hours, eat for 8

Simple for anyone to follow

16 hours is a long enough window to see significant benefits

Some people might find 16 hours too long to start

24-Hour (Eat-Stop-Eat)

Fast for one or two 24-hour periods a week

Longer fasting windows for more health benefits

24 hours might be too long of a fasting period for some

5:2 Method

Eat normally five days a week, and limit calories to 500-600 two days a week

Allows you to eat some food even on fasting days

Counting calories gets complicated

Alternate Day

Every other day you limit your calories, but you don’t cut out food entirely

Good if you’re nervous about the idea of cutting out all food

Still gives you some nutrition during fasting times

Likely the least effective for weight loss and other benefits of fasting

Fasting Mimicking

For five days, you have very limited calories that trick your body into thinking it’s fasting

You can still feed your body, so you may feel better overall

Great for weight loss

If you buy the Prolon fasting-mimicking program, it’s expensive

Five days is a long time for some

The Warrior Diet

Consume minimal calories from raw fruits and vegetables during the day, and have a large meal at night

You can have some food throughout the day and you’re likely to increase your fruit and vegetable intake

You have to follow a Paleo-style diet when you do eat

Sporadic Meal Skipping

You can skip meals whenever you feel like it works for you

It’s easy and flexible with whatever you have going on

You may not get long enough periods of fasting for significant benefits

Extended Fast

For anywhere from 48-72 hours you might dry fast or water fast with no calories

This is going to give you the most weight loss benefits, and help with reversing chronic disesaes and inflammation

Extended fasts can be very difficult to maintain

 

You can also experiment to find what works for you.

Type of Intermittent Fasting #1: 16/8 Method

The 16/8 method is the most common type of intermittent fasting. It’s pretty easy to do, so people like that element.

Key features of this type of intermittent fasting include:

  • You fast each day for around 16 hours
  • Your eating window is 8 hours every day
  • You can usually fit in two or three meals in an eight-hour eating window pretty easily
  • Sometimes this method is known as the Leangains protocol
  • The 16/8 method is straightforward. You can stop eating after dinner and then skip breakfast. For example, if you can finish your dinner by 8 p.m. and then you don’t eat until noon the following day, you’ve done it.
  • You can drink water and other beverages with no calories to reduce your hunger.
  • When you are in your eating window, choose healthy foods. Don’t use fasting as an excuse to consume too many calories or processed foods.

This method of fasting is best if your biggest goal is simplicity, and you don’t want fasting windows that are too long. It’s a good starting point if you’d like to explore the benefits this style of eating could have on your life.

Type of Intermittent Fasting #2: 24-Hour Fasts

Sometimes you’ll hear this method referred to as Eat-Stop-Eat. Features of this method include:

  • You do a 24-hour fast once or twice a week.
  • You could, for example, fast from dinner one day to dinner the next, and you’ll get in a 24-hour window of fasting.
  • You can have zero-calorie beverages, such as black coffee when you’re fasting. 
  • The benefit is that your body can start going into the fasting mode, where the cellular repair happens deeper.

The benefit of this type of fasting is that you don’t have to do it every day. If you can hold out for longer periods of time, you only have to do it once or twice a week, and you can normally eat the rest of the time.

The downside is that 24 hours can be long for some people.

Type of Intermittent Fasting #3: The 5:2 Method

Features of this option include:

  • The 5:2 diet indicates you eat normally five days of the week.
  • Then, you restrict your calorie intake to 500 to 600 calories for two days out of the week.
  • This is also sometimes called the Fast Diet.
  • Women should eat 500 calories on fasting days, and men should eat 600.

In my opinion, this type of intermittent fasting gets complicated, so if you’re not a fan of that, it might not be best for you. Not having to count calories is one of the advantages of fasting, and with the 5:2 model, you still have to do that.

Type of Intermittent Fasting #4: Alternate-Day

In an alternate-day model, you do the following:

  • You fast every other day
  • There are a lot of variations of this. For example, some will allow for 500 calories on your fasting day.
  • Alternate day fasting tends to be the least effective to help with weight loss or maintenance based on research if you have some calories, but alternating full-day fasts can be extreme.
  • You’re having to go to bed hungry several nights a week, making this uncomfortable and potentially unsustainable.

Type of Intermittent Fasting #5: Fasting Mimicking

Prolon is a company that offers an option that could be more accessible for you if you don’t know if you could truly fast for an extended period of time. It’s called fasting-mimicking, and if Prolon is too expensive, you could also try to replace this on your own.

The idea is that you’re restricting your calories for a period of time so that your body essentially is tricked into thinking it’s fasting.

The Prolon Fasting Mimicking Diet includes low-calorie pre-packaged meals. Dr. Valter Longo created the Fasting Mimicking Diet, and he wanted to give the body the benefits of fasting but still provide nutrition. There are clinical studies on this protocol.

When you order a Prolon kit, it will include five days of pre-packaged meal kits low in carbs and protein but high in healthy fats.

The calorie restriction helps mimic your physiological response to traditional fasting, including fat loss, reduced inflammation, and cellular regeneration. You do this fast for five days.

The Prolon kits include nut bars, algal oil, soup blends, and herbal tea. They also include dark chocolate crisp bars, kale crackers, olives, and powdered vegetable supplements. There’s an energy drink that you use on days two through five.

If you’re okay with spending the money, this can be a convenient and effective way to fast, and it’ll help make sure you stay nourished and hydrated.

Type of Intermittent Fasting #6: The Warrior Diet

The Warrior Diet was made popular by Ori Hofmekler. When you follow this diet you:

  • Eat small amounts of fruits and vegetables throughout the day
  • You have one big meal at night
  • The idea boils down to fasting all day and feasting at night
  • You have a four-hour eating window
  • The food choices you can have on the Warrior Diet are similar to paleo

If you like the idea of at least having a bit of food during the day, the Warrior Diet is a good option. The downside is that even during your eating window, you’re restricted to foods in line with the Paleo Diet, making it more complicated.[13]

Type of Intermittent Fasting #7: Skipping Meals When You Feel Like It

The good thing about intermittent fasting, in general, is flexibility. You can simply skip meals when you want to, and you’re going to get some of those benefits.

For example, maybe you come home from work and don’t feel like cooking. Instead of ordering takeout, you could skip a meal.

How Long Do You Have to Fast to Get the Benefits?

Since you can customize a fasting schedule to whatever works for you, you might wonder how long you need to go without eating to make sure you’re going to see the benefits and results.

Everyone is different as far as how long it takes them to start to see the effects. For example, if you’re doing physical activity or have a healthy gut, you may see benefits sooner. If you’re also eating well when you can have food, you will see more results.

There are also just individual differences that play a role.

  • Most experts agree that you need to fast for a minimum of 12 hours to see the benefits.
  • Less than 12 hours isn’t going to do much.
  • If your goal is to enter ketosis or autophagy, you’re probably going to need more than 12 hours.
  • To maximize the benefits you see, you might want to shoot for anywhere from 14 to 18 hours of fasting. This is a time frame that will give you more significant weight loss benefits, but it’s still attainable. You can also go into ketosis within this window.
  • If you want to reduce inflammation and oxidative stress and induce autophagy, you should try to fast for at least 24 hours.

What About An Extended Fast?

Another available option is to do extended fasts, perhaps once every few months. An extended fast might be 36-72 hours for most people. You can drink water and zero-calorie beverages during this time, but nothing besides that. Longer fasts done infrequently may be the best way to help reduce the risk of chronic diseases.

A bigger thing to think about is what will allow you to keep up the habit. If a longer fast just isn’t attainable for you, then don’t do it. Listen to your body if you do decide to try intermittent fasting.

You might also find that after a period of doing the same type of fast repeatedly, your results plateau.  If that happens, you can switch it up.

Final Thoughts

First, you should speak to your health care provider before trying any type of fast. If you decide to give it a shot, the 16/8 approach is a good starting point. It tends to be realistic for most people and fairly safe, but the 16-hour fasting window should give you most if not all of the benefits of fasting in general.

If you’ve ever experienced disordered eating, following an intermittent fasting schedule might not be a good option for you. 

You might decide from there you want to do occasional 24-hour fasts, or maybe more extended fasts, depending on what you think your body can handle.

 

References & Peer-Reviewed Sources

[1] https://health.mountsinai.org/blog/beyond-weight-loss-the-benefits-of-intermittent-fasting/

[2] https://www.health.harvard.edu/blog/intermittent-fasting-surprising-update-2018062914156

[3] https://www.mayoclinic.org/healthy-lifestyle/nutrition-and-healthy-eating/expert-answers/intermittent-fasting/faq-20441303

[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7021351/

[5] https://pubmed.ncbi.nlm.nih.gov/34474513/

[6] https://pubmed.ncbi.nlm.nih.gov/26374764/

[7] https://www.annualreviews.org/doi/full/10.1146/annurev-nutr-071816-064634#_i24

[8] https://pubmed.ncbi.nlm.nih.gov/30897855/

[9] https://www.sciencedirect.com/science/article/abs/pii/S0969996106003251

[10] https://www.sciencedirect.com/science/article/pii/S1550413118305126

[11] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7474734/

[12] https://www.frontiersin.org/articles/10.3389/fnut.2020.570235/full

[13] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6836017/

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