What Is Intermittent Fasting?

Intermittent fasting is becoming more and more popular among athletes, those with specific health conditions, and even members of the general public.

Why is that? In the article that follows, we will be discussing common styles of intermittent fasting, the science of intermittent fasting, how to start, and why you may want to try it.

We will also go over the history of intermittent fasting, how to measure success while trying to eat in this way, and other lifestyle changes you can make alongside intermittent fasting for the highest rate of success possible.

The 16/8 method

The 16/8 method of intermittent fasting involves fasting every day for a period of 14 to 16 hours. This means that your eating window is restricted to eight to ten hours.

During the eight to ten-hour eating window, you can consume two or three meals or even more if you would like.

This method of intermittent fasting is also called the Leangains protocol. It was popularized by a fitness expert named Martin Berkhan.

This tends to be the most popular method of fasting because all it requires is not eating anything after dinner and then skipping breakfast the next morning.

If you finish your dinner at 7:00 p.m. and eat breakfast at 11:00 a.m. the next day, this is a 16 hour fast.

It is recommended that women fast for just 14 to 15 hours. This is because females appear to have better benefits of fasting from shorter fasts as compared to their male counterparts.

The 16/8 method may be easy to incorporate into the lives of those who habitually skip breakfast. However, if you are the type of person who tends to get hungry in the morning, the 16/8 method may be challenging for you.

The 16/8 method does allow for non-caloric beverages, such as water, tea, and coffee, as long as no milk, cream, or sugar is added. Consuming these beverages help to reduce feelings of hunger during the fast.

It’s not just about the timing of your meals, however. This method simply won’t work if you are overconsuming junk food and calories during the eating window. It’s essential to consume good-quality calories.

The 5:2 diet

The 5:2 diet involves fasting for two days a week. This isn’t a complete fast, however. It is simply recommended that you do a calorie restriction of between 500 and 600 calories per day on fast days.

This diet was popularized by Michael Mosley, a British journalist. It is also called the Fast Diet.

It is recommended that males consume 600 calories per day on fasting days and that females consume 500 calories per day.

This usually adds up to two small meals on fast days. For the other five days of the week, you can eat normally.


The eat-stop-eat method of intermittent fasting involves fasting for 24 hours once or twice a week.

This is a true fast, where no solid foods are allowed during the fasting period. Water, coffee, and other beverages without any calories in them are allowed while fasting.

Brad Pilon, a fitness expert, first popularized this fasting schedule.

The eat-stop-eat method is difficult for most people to follow. This is why it is often recommended that you start with 14, 15, or 16 hours of fasting and then move upward from there.

If you are trying intermittent fasting for weight loss, you must eat the same amount of food during eating periods as you would normally. In other words, don’t overconsume between your fasts.

Alternate-day fasting

In alternate-day fasting, people fast every other day. There are actually several ways of doing the alternate-day fasting diet. Some versions allow approximately 500 calories during fasting days, while others encourage a full fast with zero caloric intake.

Several experimental studies were looking at the health benefits of intermittent fasting use some version of alternate-day fasting. However, this method is not recommended for beginners. It is also not very sustainable in the long term for regular fasting.

Warrior Diet

Fitness expert Ori Hofmekler popularized the Warrior Diet. It was one of the first main steam diets to use intermittent fasting.

This method of intermittent fasting involves fasting during the day and eating a large meal in the evening.

People are allowed to consume small amounts of raw fruits and vegetables during their daily fast.

The evening feast should happen within a four-hour window.

The Warrior Diet places emphasis on healthy diet choices within the four-hour eating window, such as whole, unprocessed, nutrient-dense foods, similar to what you would eat with the paleo diet.

Spontaneous meal skipping

This method of intermittent fasting involves skipping meals as it is convenient, for example, when you don’t feel hungry or have a busy day.

It is not true that you need to eat every few hours. Human bodies are designed to withstand periods of fasting, and will not hit “starvation mode” or lose muscle if not being fed every few hours.

We can skip a meal or two from time to time without detrimental effects on our bodies and minds.

When you are consuming meals, it is important to eat healthy foods during these times.

What should you consider when choosing an intermittent fasting diet?

When you are choosing an intermittent fasting diet, you may want to consider asking yourself the following questions:

  • Do you get hungry in the morning, or are you a breakfast skipper?

  • What is your reason for intermittent fasting? Is it to lose weight, for fat loss?

  • Do you have a specific health condition?

  • Do you have good self-discipline?

  • Have you ever tried fasting before?

  • What challenges did you have?

  • Are you busy, on the go, or in a rush in the morning?

If you drink coffee or tea, you may want to consider drinking these black. If you drink coffee and tea black, they are then regarded as non-caloric beverages and are therefore allowed while fasting to help you to curb your appetite.

How long can you safely go without eating?

One study looked at varying lengths of fasts and the adverse effects related to them. They categorized the adverse effects as follows:

Grade 1: nausea, headache, insomnia, back pain, indigestion, and fatigue

Grade 2: feeling faint

Grade 3: high blood pressure

Fast length was categorized as follows:

  • Short fast: 2-7 days

  • Medium fast: 8-14 days

  • Long fast: 15-21 days

  • Extended fast: 22 or more days

Researchers found that day five of fasting had an estimated cumulative incidence of experiencing any adverse effects at grade 2 or higher.

In their research, there were two serious adverse events due to fasting that required hospitalization.

One of these was a grade 3 dehydration event. It occurred on day three of fasting in a 73-year-old male patient. He experienced headache, fever, and high blood pressure. He was taken to an emergency facility, where he received antibiotic treatment for a possible lung infection.

He also received IV electrolytes to manage the dehydration. He was then kept under inpatient observation for three days and ended up fully recovering.

The other was a grade 4 hyponatremia event, meaning the patient had low sodium. This occurred on day nine of fasting in a 70-year-old male patient. He had difficulty with speech and was immediately taken to an emergency facility via ambulance. There, he received IV electrolytes and was kept under inpatient observation for four days. He also recovered fully.

What does research show about intermittent fasting?

Research has demonstrated that there are several benefits of intermittent fasting.

Research has shown that intermittent fasting can help to lose weight. It does this not only in people who are overweight or obese but also those who are of normal, healthy weight.

It also helps to reduce body fat, visceral fat (the fat around your organs that is most closely associated with heart disease risk), and the levels of total cholesterol and triglycerides in the blood. It helps in the treatment of the metabolic syndrome.

It also improves metabolic health via its effects on the gut microbiome and modifiable lifestyle behaviors, such as sleep.

Intermittent fasting has also been found to improve functional outcome in a wide range of age-related disorders, including:

  • Diabetes

  • Cardiovascular disease

  • Cancers

  • Alzheimer’s disease

  • Parkinson’s disease

  • Stroke

After a stroke, intermittent fasting can help to prevent tissue damage and neurological deficits. This is because of intermittent fasting’s effects on suppressing oxidative stress, inflammation, and cell death pathways.

Intermittent fasting is also known to help improve insulin levels in those at risk of or with type 2 diabetes.

Intermittent fasting activates the adaptive cellular stress response signaling pathways. These pathways help to enhance mitochondrial health and the repair of DNA within cells. It also promotes stem cell-based regeneration.

Intermittent fasting has beneficial effects on physical and intellectual performance. It does this by affecting various aspects of body physiology and biochemistry. This could have applications for athletic performance.

Recent research findings have shown that immune cells are involved in brain function. They have also shown that intermittent fasting might impact the relationship between immune cell expression in the brain and cognitive deficits, such as memory deficits.

Intermittent fasting, according to research, can help to reduce oxidative stress, delay aging, and have anti-inflammatory effects.

How do you measure the success of an intermittent fasting diet?

There are several ways in which you can measure how your intermittent fasting diet is going. They include the following:

What is the history of intermittent fasting?

Fasting and other dietary regimens have been used in the treatment of epilepsy since 500 B.C., and possibly even before this.

During the Middle Ages, fasting was a practice commonly seen among religious women, in an attempt to follow a pious lifestyle. At this time, holy fasting was characterized by a refusal to eat, with no calorie intake. This could even involve binging, purging, and lack of menstruation.

When we now look back at Medieval narratives of holy fasting, we can actually see patterns that are comparable to what we would describe as eating disorders in the current day and age.

One article, in particular, was published by Guelpa and Marie in 1911. This article is often quoted in the history of dietary treatment. This research formed the basis for the use of the ketogenic diet to mimic fasting.

In this paper, 21 patients had no food but were allowed to drink unlimited water for four days. This four day fast was followed by a vegetarian diet restricted to half of the patient’s regular intake. This was the first research study performed using intermittent fasting as a treatment strategy for epilepsy.

Over the past 15 years, there has been an explosion in the use of and scientific interest in intermittent fasting.

Who can benefit from intermittent fasting?

People with specific health conditions can benefit from intermittent fasting. However, those who are healthy can benefit, as well.

Research has also found that intermittent fasting has health benefits for those who are overweight, obese, and of a healthy weight.

Specific health conditions that can benefit from intermittent fasting schedule include:

How should you approach intermittent fasting?

Select a method of intermittent fasting that aligns best with your lifestyle. Choose one that you think will suit you best.

It is usually best to start slowly and ease your way into an intermittent fasting diet. You may want to begin with a shorter fast than planned and work your way up to a full 24 hour or desired length of fast.

How often you should skip meals depends on the type of intermittent fasting plan you are following.

  • On the 16/8 diet, you are basically only skipping breakfast, but you are doing this every day.

  • With the 5:2 method, you are fasting for two days per week. It is usually best to spread them out across the week (for example, fast on Monday and Thursday).

  • On the eat-stop-eat diet, you skip 24 hours’ worth of meals once or twice a week.

  • With alternate-day fasting, every other day is a 24 hour fast.

  • The Warrior Diet involves a 20-hour fast every day.

With spontaneous meal skipping, you are skipping a meal whenever you would like to or whenever it is convenient for you. For example, if you are rushed in the morning, then you can skip breakfast.

On most of these intermittent fasting regimens, you can restrict calories rather than skipping meals altogether.

Intermittent fasting diets have become popular because they are relatively simple to follow. Intermittent fasting works because it fits quite easily into people’s schedules and routines.

Many people are non-intentionally doing intermittent fasting anyways, particularly the 16/8 and spontaneous meal skipping methods.

What lifestyle changes are beneficial alongside intermittent fasting?

Exercise is beneficial alongside intermittent fasting. This is because exercise helps to curb your appetite and keep energy levels up. These are often side effects that occur when fasting or restricting calorie intake or working on weight loss and fat loss.

If you are intermittent fasting, you may also want to drink lots of water. Besides helping you maintain hydration, water is a non-caloric liquid that you are allowed to consume while fasting. It can help to make you feel more full during a fast.

When you are between fasts, make sure that the food you are consuming is whole, healthy, and unprocessed. This is important for everyone, but especially those using this diet to help them lose weight, improve cognitive function, and for those with obesity and diabetes.

Who should avoid intermittent fasting?

Intermittent fasting may not be right for those with a history of eating disorders, those with low blood pressure or a tendency to faint, or the elderly. It’s always good practice to check with a health care provider before trying intermittent fasting to make sure it’s right for you.

Intermittent fasting has been adopted by people of all genders, ages, and with varying health concerns. And for good reason, too. Ask your health care provider if intermittent fasting is the right choice for you.

Then consult the guidelines above to start your intermittent fasting diet for the highest chance at success.

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Whether you are considering this method of eating for weight loss, improved cognitive function, diabetes management, preventing cardiovascular disease, or any of the other reasons to try this diet, we wish you the best of luck.


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