Guide to Intermittent Fasting

Many people all around the world struggle with weight loss and muscle growth, often resulting in absurd diets and unhealthy, sometimes even dangerous fasting methods to reach their goals. These actions can be damaging to the human body and are not the most effective ways to lose weight, sometimes even being counter-productive.

Fasting is not a new trend as humans have actually been fasting in the past. Intermittent fasting is not a diet plan, but it is an eating pattern where you cycle between periods of eating and fasting. It is proven that following one of few intermittent fasting methods regularly can result in weight loss and muscle building.

What is Intermittent Fasting?

Intermittent fasting is not a diet plan, but it is a dieting schedule. It does not tell you what to eat, but it does tell you when to eat.

Fasting is defined as the voluntary avoidance of food for long periods of time. Intermittent fasting is based on skipping some meals on purpose. This means consuming most of the day’s calories in some specific time window and not eating during most of the time that you are awake. There are few intermittent fasting patterns, but the most common involve daily 16-hour fasts, or fasting for 24 hours, once or twice per week.

It is a great way to get lean without going into some crazy dieting plan or cutting calories to nothing. In fact, it is the opposite – when you start intermittent fasting, you try to keep about the same amount or a bit more calories for each meal. However, by skipping an entire meal each day, you are, on average, consuming fewer calories per week. Intermittent fasting is also a good way to keep your muscle mass the same while losing the fat; just make sure to keep your protein intake high enough.

Fasting is not a new trend; people have practiced various forms of fasting in accordance with their religious (including Christianity, Islam, and Buddhism) and cultural beliefs for centuries, and some cultures still adhere to strict fasting practices for these reasons.

Some people fasted because there was no food available on a consistent basis. In very old days, our hunter-gatherer ancestors didn’t have shops, refrigerators at home or food available year-round. Human bodies evolved to be able to function without food for extended periods of time. If you think about it, occasional fasting is more “natural” than constantly eating a few times per day.

You are doing “fasting” every day already (or actually at night) while you sleep. Intermittent fasting can simply be extended by not eating for longer periods of time. You can do that by skipping breakfast and eating your first meal later in the day – at noon – and have your last meal late in the evening at around 8 pm.

This eating pattern will give you 16 hours of fasting every day and restrict your eating time window to 8 hours. This is one of the most popular forms of intermittent fasting – the 16/8 Method.

Benefits of Intermittent Fasting

Many studies have been done on intermittent fasting in both animals and humans. Studies have shown that it can have powerful benefits for weight control, the health of your body and brain, and it may even help you live longer.

You can watch Dr. Mercola outlining the main benefits of intermittent fasting:

Here are the main benefits of intermittent fasting:

1. Losing Weight and Building Muscle

Fasting promotes higher growth hormone secretion and stronger insulin sensitivity, which are the keys for losing weight and building up muscles. Intermittent fasting is often considered to be the ultimate fat loss diet that’ll have those excess pounds melting off you in minutes. That’s not exactly true – fat loss comes down to a caloric deficit which intermittent fasting can make easier for you to implement.

We all know that not all calories are equal, but cutting some calorie intake plays a key role in losing weight. When you fast for 16 hours per day, or 24 hours every few days, you are also making it easier to restrict caloric intake over the course of the week.

That pattern provides your body a chance to lose weight as you are just eating less calories than you were consuming before (given that your meal caloric intake is not increasing significantly). If you keep on holding this pattern for long enough, it can lead to consistent weight loss and sustaining it.

Fat loss and muscle gain are two of the main reasons why people start intermittent fasting, but it isn’t the only reason to try intermittent fasting. There are many health benefits that this method provides.

2. Helps You Live Longer

There are some studies which prove that occasional starving extends years of life. When you’re starving, your body finds ways to extend your life.

However, by taking the intermittent fasting approach, you don’t need to starve. It does provide all the benefits associated with starving, while at the same time allowing you to split time in fasting and feasting times.

Intermittent fasting may also reduce some of the risk factors associated with heart disease: blood triglycerides, inflammatory markers, LDL cholesterol, insulin resistance, and blood sugar.

Some scientific studies show reductions in markers of inflammation, which is a key driver of many chronic diseases.

More efficient immune system, slower metabolic rate, better protein production, and the increased production of hormones contributes to this long-term benefit of fasting. In addition to the Human Growth Hormone that is released more frequently during a fast, an anti-aging hormone is also produced more efficiently.

3. Reduces Risk of Cancer

There hasn’t been a lot of research and experimentation done on the relationship between cancer and fasting, so this is debatable at this point. However, there are some animal studies which suggest that intermittent fasting may help prevent cancer.

This latest study on mice suggests that a low-calorie fasting-like diet, in addition with chemotherapy, enables the immune system to recognize and kill skin and breast cancer cells. Another study confirms that the side effects of chemotherapy may be diminished by fasting before treatment.

4. Makes Your Day Simpler

Many of us don’t want to put extra complexity in the already busy days we have. Intermittent fasting provides additional simplicity to your life. After you wake up, you don’t need to worry about breakfast. You just grab a glass of water (preferably lemon water) or a cup of coffee and you are good to start your day.

Intermittent fasting causes you to skip your usual meal, which means one or two less meals to plan, shop for and prepare, and you only eat during your eating time window. It is one less decision you have to make every day.

5. Levels up Your Brain

Some people are claiming that if they don’t eat in the morning, they feel anxious in the beginning of the fasting period. This feeling fades away after a few days, and it transforms into feeling much more focused, alert and productive in the morning.

They claim that, by fasting, you may find yourself feeling lighter with more energy, particularly during workouts or any other physical activity. Your attention to detail, motivation and overall productivity may be boosted. While reading a book or writing a research paper, you may find yourself working far more efficiently when in a fasted state.

Mark Mattson is a leading expert on intermittent fasting. He is a professor at Johns Hopkins University and Chief of the Laboratory of Neurosciences at the National Institute on Aging. In this TEDx talk, Mark provides quite a good overview of intermittent fasting, and it is highly recommend to watch it in case you would like to get more arguments in favor of using it:

6. Easier Than Dieting

According to a survey carried by the United Kingdom food company, of those who diet regularly, two out of five quit within the first seven days, one out of five last a month, and just 20% make it to the three-month mark. The main reason most diets fail is not because people tend to switch to unhealthy foods, but because it is very hard to follow it over a long period of time. This is more a behavioral change problem rather than a nutrition problem.

One great benefit of intermittent fast is that it is very easy to implement as soon as you get over the idea that you need to be eating all the time. According to some studies, intermittent fasting is an effective strategy to help people with a high fat percentage of their body to lose weight. The study concluded that people tend to quickly get used to a fasting routine.

How Intermittent Fasting Works

In order to comprehend how the intermittent fasting method leads to fat loss, we need to understand the main differences between the feeding state, when you eat, and the fasting state, when you don’t eat or you consume very little food.

Your body is feasting when it is digesting and absorbing the food you just consumed. This state starts from the moment you begin eating and lasts for about three to five hours until your body digests and absorbs the food you ate. In feasting state, it is very difficult for your body to burn fat because the food you just ate causes your insulin levels to get high.

After that state, your body switches to the fasting state when your body is not processing any food. During this state, your body doesn’t have a recently consumed meal to use as energy, so it is more likely to start burning fat stored in your body, which was inaccessible in the feasting state as it becomes the only energy source available. The fasting state usually lasts until eight to twelve hours after your last meal. In this state, it is much easier for your body to burn fat because your insulin levels are low.

Our body is very rarely in this fasting mode because of the quite long time – up to 12 hours – it takes for the human body to switch to the fat burning state. That is one of the main reasons why people who start using this eating pattern experience losing fat without actually changing what they are eating or how much they are exercising.

Intermittent fasting

Examples of Intermittent Fasting Eating Schedules

Intermittent fasting is not a diet but rather an efficient eating pattern. There are many ways this method can be applied. Here are most popular ways to do intermittent fasting.

1. The 16/8 Method (Lean Gains)

The 16/8 Method, otherwise known as Leangains model, uses a 14-16 hour fasting window, which then turns into a 8-10 hour eating period. This fasting model was introduced by Martin Berkhan from, and that is why it is associated with that name.

The advantage of this method is that you have your last meal of the day in the evening and then most of the fasting period lasts while you sleep. After you wake up, you just extend the period without food for an additional 4-8 hours. For example, you had your last meal at 8 pm, slept at 12 am, and woke up at 8 am. You’ll eat your first meal at noon, and this will yield 16 hours of time without food.

This method could be difficult to adapt for people who like to eat breakfast. However, after a few iterations, this habit is not that difficult to break. If you are already not a big fan of eating in the morning, then the adoption of this method will be very easy. During the fasting period, to reduce hunger levels, you can drink water, coffee and other non-caloric beverages. You can add milk or a little cream to your coffee, but try to avoid adding sugar!

During the eating time window, it is recommended to mostly eat healthy food. This pattern will not yield any positive results if you will be eating lots of junk food or consuming an excessive amount of calories during your feasting stage.

16/8 lean gains method

2. Eat-Stop-Eat (2×24 Week Method)

The best way to start with intermittent fasting is considered to do it once a week. It shows that the occasional fast leads to many of the benefits of the intermittent fasting, so even if you don’t cut down calories consistently, you still will get many of the health benefits provided by fasting methods.

In this Eat-Stop-Eat method, you fast for a full day once or twice a week. This method was introduced by fitness expert Brad Pilon, and has been quite popular for a few years.

The main idea with this pattern is that you fast for a full 24-hour period. For example, you have a breakfast at 8 am today, and then you can start eating the same time again tomorrow. If you prefer, you can do the same pattern for having dinner and then fasting all the way to the same time tomorrow.

Eat-Stop-Eat (2×24 Week) Method

Coffee, water and other beverages with a low amount of calories (and no sugar) are allowed during the fast, but you need to keep away from solid food. If your goal is to lose weight, then it is very important to stick to what you have been eating normally during the eating periods and the same amount of food as if you hadn’t been fasting at all.

Stopping eating for a full 24 hours can be quite difficult for many people. However, you don’t necessary need to carry 24 hours from the start. You can begin with doing 14-16 hours and then move up from there.

3. Alternate Day Fasting

The alternate day intermittent fasting pattern consists of fasting every other day throughout the week. There are various versions of this intermittent fasting method. Some of those methods allow about 500 calories during the fasting days, whereas others don’t. Many of the scientific studies showing health benefits of intermittent fasting used some version of this.

Alternate Day Fasting

This fasting method is considered quite extreme; therefore, it is not recommended for beginners.

The advantage of this alternate day intermittent fasting method is that it gives you a longer time in the fasted state than the 16/8 method of fasting. In theory, this way, it would increase the benefits you receive from fasting.

In practice, according to James Clear, the concern is eating enough. The main hard part of intermittent fasting is to teach yourself not to consistently eat more. It is okay to eat a bigger meal once, but do not do it consistently during feasting periods. By keeping the same number of calories per meal, you end up losing weight, because you usually end up consuming less calories. You cut out some meals from the week, but the size of the meals that you are having stays the same.

Depending on your goals, this could be the advantage, but if you will be fasting multiple times per week and eating the same size meals during the feasting period, you could end up consuming quite a lot less calories during the week.

It is considered a better idea to use the daily intermittent fasting pattern or 24-hour fasting periods once per week (or per month) rather than multiple 24 hour fasting periods per week.

4. The 5:2 Diet (Fast Diet)

The 5:2 diet, also called the Fast Diet, as the name implies, consists of eating normally for 5 days and limiting consumption calories for 2 days per week to 500-600 calories per day. This diet was popularized by British journalist and doctor, Michael Mosley.

The 5:2 Diet (Fast Diet)

During fasting days, it is recommended to consume 500 calories per day for women and 600 calories for men. This calorie consumption can be divided into two or several meals. For example, during fasting days, you can have two small meals of 250 calories each for women or 300 calories for men.

5. The Warrior Diet

The idea of the Warrior Diet is to eat small amounts of raw fruit or veggies, fresh juice, and a few servings of protein during the day, then eat one huge meal at night. This diet was popularized by fitness expert, Ori Hofmekler.

This eating pattern means that you fast for the whole day and then feast for a maximum of a 4-hour window. The Warrior Diet was one of the first popular “diets” to include a form of intermittent fasting. The benefit of this eating pattern is that you can still have small amounts of food even on the fasting period. People who regularly practice this diet report increased energy levels and a fat loss.

The Warrior Diet

The difference from other intermittent fasting methods is that the Warrior Diet emphasizes specific food choices that are similar to a paleo diet. These guidelines for what you need to eat (and when) can be hard to follow long-term. If you aren’t used to eating large meals at night, this eating pattern can be very difficult to adopt. Good that you have many other intermittent fasting methods to choose from.

6. Random Meal Skipping (Skipping Meals When Convenient)

To reap fasting benefits, sometimes you don’t even need to follow some methodical fasting plan. You can, from time to time, skip a meal or two, especially when it is convenient – you don’t feel hungry or don’t have time to cook and eat.

The human body is well-equipped to cope with hunger as mentioned above, be it skipping a meal or running for even longer periods without food. Saying that people need to have food every few hours or they lose muscle is a myth.

If you don’t feel hungry or you’re travelling and don’t have time to eat, you can skip that meal and put yourself on a little fasting period. Skipping some meals when you feel like doing so or have the right conditions is a form of spontaneous intermittent fasting.

Just don’t forget to eat healthy food when you are eating after fasting period. Junk food or food heavy on fat will not provide you with any of the benefits you expect from intermittent fasting.

Who Can Benefit from the Intermittent Fasting and Who Will Not?

It depends on each individual, such as your body composition, personal goals and personal lifestyle.

Intermittent fasting will benefit you if you are 15-20% body fat or higher and looking to trim some fat and get a better athletic look. If you don’t like to eat in the morning, then intermittent fasting will be very easy to adopt and regularly practice, especially the 16/8 Method where you skip breakfast and eat during the afternoon hours.

You will not benefit from intermittent fasting if you are already lean or if you struggle to add some healthy weight. If you are trying to maximize adding muscle to your body, then intermittent fasting is definitely not for you. It will not be a good idea to fast if your job is very physically active, as you might struggle to keep your energy high enough without consistent food consumption.

Intermittent fasting

Words of Precaution Before You Dive Into Intermittent Fasting

Even though the human body is designed to cope with hunger for some periods of time, there are some precautions to take before you commit to intermittent fasting. If you are considering some form of fasting, make sure to discuss it with your doctor. Skipping meals and severely limiting calories can be dangerous for people with certain conditions like diabetes. People who take diuretics for blood pressure or heart disease also may be more prone to electrolyte abnormalities from fasting.

There are many doctors who warn against fasting for some long periods of time without the supervision of a specialist. Some doctors today still deny many of the points mentioned above and claim that fasting is detrimental to one’s health and have evidence to back their statements.

Frequently Asked Questions About Intermittent Fasting

1. Am I allowed to drink liquids during fasting?

Yes. You can drink coffee, tea and any other non-alcoholic drink, as long as it does not have sugar in it, but you can add a small amount of milk or cream to your coffee or tea. Coffee is particularly good to drink during fasting periods, because it reduces the feeling of hunger. Water is a must to drink during fasting periods.

2. I have read that you need to eat breakfast to stay healthy. Is it true?

No. Your body knows how to deal with extended periods without food. There is a myth that you need to have breakfast, because most of the stereotypical individuals who skip breakfast are living an unhealthy lifestyle.

3. I thought you need to eat every 3 hours to lose fat?

This idea is based on the logic that your body burns calories while processing food, so if you eat more frequently, you’ll also burn more calories, and while eating more meals, you burn more calories throughout the day. The problem with this is that you burn a proportional amount of calories to the size of your total meal size for the day. So you will spend the same amount of energy processing 5 meals by 400 calories as 2 meals by 1000 calories. There is no difference in how many calories you burn by digesting smaller but more frequent meals if the calorie amount is the same as less frequent larger meals.

4. Can I run or work out during fasting period?

Yes, running or working out while fasting is fine. Scientific studies show that exercising in a fasted state can supercharge your body’s fat-burning potential.

5. Will I lose muscle because of fasting?

Intermittent fasting is one of the methods to lose weight. Any weight loss methods can cause loss of muscle mass. That is why it is important during the fasting period to work out and keep protein intake high.

Have other questions? Please ask in the comments.

Intermittent fasting

How to Start

It depends on your current eating habits and patterns. Some people might already be doing fasting by not eating breakfast in the morning.

Most people choose to start with the 16/8 Method and skip breakfast. This way, you can have dinner with your family and friends, so it won’t clash with your social patterns. Another good way to start is the Warrior Diet, because you can still have small amounts of fruits and veggies part of the day and then have a single large meal in the evening.

After you’ve done the 16/8 Method for a while and you find that it is easy to follow and you feel good during the fast, then you can try moving on to more advanced fasting methods. Those could be one 24-hour fasting period per week (Eat-Stop-Eat method) or eating normally for 5 days and then limiting consumption of calories for 2 days per week to 500-600 calories per day (5:2 Diet).

Another way to start and do fasting periods is to skip meals whenever you feel like, for example, if you are too busy to eat or don’t have the right conditions to have a meal, like during travelling.

To find your way in intermittent fasting, you need to experiment and find what fits best. Each of us is an individual with very individual schedules and habits, and there is no golden rule for how to start, so you need to experiment for a bit and then go further from there.

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