What Fasting Really Is 

What is fasting? According to Britannica, it is defined as “abstinence from food or drink or both for health, ritualistic, religious, or ethical purposes.” The definition goes on to say that this abstinence may be long-term or of a shorter duration. 

Fasting has been practiced in locations around the globe for thousands of years. It has been done by culturally designated individuals (such as candidates for initiation rites), followers and founders of a variety of religions, and groups and individuals who are protesting political, ethical, or social principles. 

For the purposes of this book, we’ll be largely focused on fasting for health purposes. This is the choice to engage in fasting to gain some form of health benefit. One person might choose to fast as a way to feel healthier in general, while another may be focused on fasting for weight loss. 

This chapter of the book will look at what fasting is, from how much time it takes to start to how long it should last. We’ll look at goals around fasting, whether fasting is uncomfortable, and what kinds of fasts are used in today’s modern world. In addition, we’ll share a short history of fasting so you can see just how long this practice has been in place. 

A Short History of Fasting 

When you look back into history, there isn’t any time when it is clear that humans did not fast. Written works from various locations, religions, and cultures indicate that some people fasted throughout history. It has long been a practice associated with spirituality and health. 

Some of the earliest civilizations known to engage in fasting include the ancient Greeks, ancient Indians, and ancient Egyptians. The accounts from these long-gone days show that fasting was a way of strengthening the spirit. However, it was also a solution to prevent and cure a variety of health issues. 

Looking back at the early Greeks, fasting has come a long way but it still holds many similarities to that of earlier cultures. For instance, the Greeks abstained from all forms of food, and the only beverage they consumed while fasting was water. This is similar to forms of fasting that remain popular today.

As far back as 580 to 500 BC, Pythagoras would starve himself for 40 days at a time. The lauded philosopher and mathematician believed that fasting was a means of increasing creativity and mental perception, something that scientists now agree is true. Also of note was that Pythagoras (and his followers) were vegetarians. 

As a disciple of Socrates, Plato (427 to 347 BC) separated medicine into ‘false’ and ‘true.’ The medical practices that were considered true include the sun, the air, and fasting. 

However, Hippocrates (460 to 357 BC), who is considered the father of modern medicine, would be the person who designed the Mediterranean diet. Fasting would no longer be relegated to the world of philosophy and would instead move into the medical realm. 

One quote from Hippocrates reads as follows: “The addition of food should be much rarer since it is often useful to completely take it away while the patient can withstand it until the force of the disease reaches its maturity. If the body is cleared, the more you feed it, the more it will be harmed. When a patient is fed too richly, the disease is fed as well…excess is against nature.” 

As someone without medical training, I can look at the way we lose our appetites when we’re ill. It seems that Hippocrates knew how the human body was tuned by nature itself. 

The ancient Greeks realized that fasting for certain periods could cause less severe and more infrequent seizures for those who had epilepsy. It was a form of treatment for this condition, as anticonvulsant drugs didn't reach the market until the 1950s. 

The Bible also mentions fasting, with notes about 40-day fasts for individuals like Jesus, Elijah, and Moses. Apostle Paul gave indications of the fast and focused his preaching on keeping Passover. 

E.H. Dewey, MD, made claims in the mid-1800s that most illnesses of humans are related to diet. He published his thoughts in The True Science of Living. This helps create a larger following for prolonged fasting. 

Other cases that were recorded in medical literature in this period include: 

● 1880 – Tanner fasted for 40 days. 

● 1887 – Alexander Jacques fasted for 30 days. 

● 1890 – Signor Succi fasted for as long as 40 days. 

Moving into the 1990s, researchers had a huge interest in how fasting could be used for weight loss. Folin and Denis started to recommend short fasting sessions in 1915 as a safe form of weight reduction. Longer fasting periods were only recommended for those with extreme cases of obesity. 

Intermittent fasting first made an impact in 1945 when it was determined it extended the life of mice. It became popular among humans in the 2000s and has since been seen as a great alternative to the starvation diets of the 1800s. Popular cycles include the 14:10 and 16:8 methods where you fast for 14 to 16 hours and then eat during the remaining eight to 10 hours. 

In all times of history, fasting has been present. It isn’t always easy to determine the motivation or reasoning for fasting, but it often comes down to one of three reasons. These include fasting as an act of supplication, fasting as an act of purification or penitence, and fasting to prepare for a crucial moment in a group or person’s life. 

What Is Your Goal with Fasting? 

Most people’s main goal with fasting is to cleanse the body and the soul. However, some focus on one aspect more than the other. While fasting can be a challenging process, it allows people to strengthen their willpower and work on their traits of perseverance and patience. 

In general, fasting is a way to improve overall health. It can also be used to regulate and cleanse the body. What is your own goal with fasting? Have you thought about it? Written it down? Shared it with those around you? 

No matter your answer to those questions, you have a reason why fasting appeals to you. That’s personal and there is no wrong answer. 

Perhaps you want a body that can handle stress. Maybe you just want to lose a few pounds by cutting down on the times and dates when you consume calories. Your reason is your own, but you should know what it is, even if nobody else does. 

There’s a purpose for having this front and center before you start your first fast. Your goal is to determine which type of fasting is right for you. It can also give you an idea of how many nutrients and calories you should be consuming. 

After your goal is set, you can choose a type of fasting to work with. Many people try several different methods when fasting for health reasons. 

The plan should be something you think you can stick to and suit your preferences. There are several types of fasting, which we’ll get into in more detail later, including time-restricted fasting, alternate-day fasting, periodic fasting, and more.

How Much Time Does It Take for Fasting to Start?

Once you start the fasting process, it takes some time for your body to realize what is happening. However, after a certain number of hours pass, your brain will start to feel clearer, and your energy will reset. 

There are many benefits to fasting, but you have to do it long enough to let things start to occur naturally. Fasting can improve your immune function, repair damage to cells, remove pathogens, reduce inflammation, and increase autophagy. It can decrease the issues associated with autoimmune diseases and increase DNA repair, even in a short period. 

If you haven’t yet visited a physician, make sure you do so before you start fasting. All of us are unique and fasting may not be right for all people in every situation. The end of this chapter will give a bit more information about why it’s so crucial to see a physician before starting a fast. 

At about eight to 12 hours after you start fasting, the sugar, glucose, and glycogen stores in the body will have had time to decrease. While those are dropping down, human growth hormones like adrenaline and cortisol will be increasing. Fasting for at least 12 hours is typically needed to change the way your metabolic system works. 

When you’re eating three times a day, the body gets energy from glucose, which is a type of sugar. Glucose is found in the beverages you drink and the foods you eat. Eating regularly ensures a constant supply of glucose since you’re eating and drinking throughout the day. 

After you fast for about eight to 12 hours, the levels go down since you aren’t eating as much. When glucose can’t be used for energy, the body will turn to the next best thing. In this case, that’s body fat. The fatty acids in the body are absorbed into the blood to create ketones. The ketones are then used for energy. 

When this happens, we call it a metabolic switch. The body switches from using glucose for energy to using ketones instead. 

When ketones are used, it can result in weight loss. This is why many people choose to fast as a method to shed a few pounds. However, this is not the only benefit you might experience from ketones. They can also have a positive impact on your body’s cells and organs. 

Getting the best results from fasting requires doing it for at least 12 hours for many people. This is because your metabolism switch won’t occur until that point. Your body will continue to use glucose for energy as long as it’s available.

Your body also may take some time to get used to fasting when you are new to it. The results you want may not occur right away. A prolonged period of fasting over two to four weeks is when many people start to feel and see the results that they wanted when they started fasting to begin with. 

Is Fasting Uncomfortable? 

I’m not going to lie to you. Not everyone finds it comfortable to start fasting. Most people will find the process a huge challenge in the beginning. However, if you persevere and show a bit of willpower, this is something that doesn’t last forever. You’ll get used to fasting and your body will start to be prepared for it to happen. 

Yes, there may be discomfort when you start fasting. But when you make it past that, you could feel better than you ever have in your life. 

Understanding the side effects that may occur during fasting will prepare you to move forward. Keep in mind that we are all unique individuals. Some people may have few to no side effects, while others may have a much more frustrating experience when starting the process. 

Cravings and Hunger 

It stands to reason that fasting, which involves not eating, leads many to feel hungry. This is likely the most common form of discomfort someone will feel when they embark on a fasting journey. 

Anytime you go long periods without consuming calories, or you cut down on the number of calories you ingest, you can expect to feel more hunger than you did before. 

In most cases, hunger is a symptom that will be experienced in the first few days of fasting. Over time, this will start to become less intense. Hunger symptoms are something the body can adapt to when you are regularly fasting and your body has been primed for that. 

Lightheadedness and Headaches 

People also sometimes experience headaches when starting fasting. This is another situation where the headaches may occur in the first few days but will slowly stop being as frustrating or frequent. 

This isn't something that every person who fasts will experience. Most of the headaches are mild, rather than moderate or severe. "Fasting headaches" tend to be located at the front of the brain, and the pain can be handled and pushed through.

If you tend to get headaches before fasting, it’s more likely you will get them when not eating. A few of the things that may contribute to headaches include caffeine withdrawal and low blood sugar, both of which can occur when you fast. 

Mood Changes Like Irritability 

Mood disturbances, especially as relates to irritability, are also something that may occur when fasting. This is totally normal. As you experience low blood sugar, it can cause feelings of irritation. 

Hypoglycemia, or low blood sugar, may happen when you are fasting or taking in fewer calories than normal. This can lead to poor concentration, anxiety, and irritability. 

Bad Breath 

Another thing that may occur when fasting that is uncomfortable is having bad breath. There is a reason that this is more common among those who are fasting. When you have less saliva flowing in the mouth and the acetone is rising, it affects the scent of your breath. 

As mentioned earlier, fasting causes the body to use fat for fuel instead of sugar. When fat is metabolized, this causes acetone to be created. This makes it more prevalent in the breath and blood when fasting. 

This also plays into dehydration, which can occur when fasting. When someone is dehydrated, the mouth becomes dry, which may cause bad breath. 

Dehydration 

When someone starts fasting, the body will release large amounts of salt and water in the urine. This is called diuresis and is natural when you start fasting. If this occurs and the electrolytes and fluids aren’t replaced, it can lead to dehydration. 

It also is a fact that many people who fast do not drink enough or even forget to drink. This is especially common for someone who is starting an initial intermittent fasting routine. 

The good news is that you can easily avoid dehydration. You can also catch it when it’s early and take care of the issue. Make sure that you drink water throughout the day and look at the coloration of your urine. It should be a light yellow color. If it’s darker, you may be dehydrated.

Malnutrition

One of the worst things that can occur when fasting isn’t done properly is malnutrition. This may happen if someone fasts for long periods and doesn’t replenish their body with appropriate nutrients. Malnutrition can also occur with badly planned continuous energy restriction diets. 

However, most people can meet all their nutritional and caloric needs while fasting. The problem occurs when fasting isn't planned carefully, or calories are very restricted. This can lead to health complications as well as malnutrition. 

This is why it’s important to eat a nutritious and well-rounded diet as part of your fasting practice. You should never try to restrict your calories to an extreme level. 

Having a healthcare professional in your corner who is well-versed in fasting can help ensure you start with a safe plan. It should help you get the right nutrients and consume enough calories to be healthy. 

Sleep Problems

Research indicates that sleep disturbances may occur among some people who choose to fast. This most commonly manifests as having trouble going to sleep or being unable to stay asleep. However, many people will not experience this problem at all. 

Studies are mixed on whether this is a problem for most people who fast as part of a healthy diet. However, you should be aware that it is possible, and it can be uncomfortable if you do experience it. 

Low Energy and Fatigue

When you practice any form of fasting, it may lead to low energy levels or feelings of fatigue. One of the reasons for this is low blood sugar. It can cause you to feel weak, tired, or both. If you experience the sleep issues we just mentioned, this can also lead to feeling more tired than usual. 

At the same time, not everyone has this side effect. Some find fasting results in less fatigue. This is often the case once your body is used to a regular period of fasting. 

Digestive Issues

Finally, some people who fast experience digestive issues. These range from bloating and nausea to diarrhea and constipation.

Since fasting involves a restriction in food intake, it can have negative effects on the digestive system. Dehydration can also make some of these issues worse, specifically constipation. It’s important to remain hydrated when fasting. Eating nutritious foods can also help prevent these side effects. 

A feeling of discomfort is normal when you start fasting, but many people experience nothing more than a feeling of hunger. Others may experience some of the other side effects noted above. However, most of these effects are mild or moderate. 

Fasting has a host of benefits, which we will go into detail about in chapter five. Most people who fast find that the benefits heavily outweigh any of the discomforts of starting a fasting regimen. It’s up to you (and your doctor) to decide if the perks of benefits are more than the risks. 

When Does Fasting End? 

We’ve covered the fact that it takes about 8 to 12 hours to move into a fasting body state. But when does fasting end? The simple answer is that a period of fasting ends when you start the refeeding process. We’ll go into more detail about how to do this in chapter seven of this book. 

To understand when fasting ends, you need to be aware of the six stages of fasting. These apply to both prolonged and intermittent fasting methods. Below are details about each stage so you can better understand the processes the body goes through when fasting. 

● Stage 1 – After eight to 12 hours, the body goes into ketosis. This is when your body will stop using sugar for energy and instead burn fat to give you the energy you need. 

● Stage 2 – At around 18 hours, the body will have fully switched to burning fat. You will be creating a significant amount of ketones. Exercising can help amplify this effect. 

● Stage 3 – Once 24 hours have passed (or sooner), your cells will be recycling components and breaking down misfolded proteins associated with diseases like Alzheimer’s. This is known as autophagy. 

● Stage 4 – With 48 hours of few to no calories, protein, or carbs, growth hormone levels will reach as much as five times as high as when the fast began. ● Stage 5 – At around 54 hours, insulin will be at its lowest point since fasting started. The body will be extremely sensitive to insulin. 

● Stage 6 – When you reach 72 hours, the body breaks down old immune cells and starts to create new ones.

The final part of fasting is breaking the fast and refeeding. This is one of the most important parts of the process. You should always break a fast using a balanced and nutritious meal that helps your cells and tissues function well. 

Different Types of Fasts

There is another factor to consider when choosing to fast: the type of fast you choose. There are two different varieties, known as intermittent fasting and prolonged fasting. Each is unique and has different benefits and requirements than the other. Below is a bit of information about what makes these fasting methods different from one another. 

Prolonged Fasting 

The human body is a wonderful thing. It has adapted to withstand all sorts of hardship, including lack of food. If you want to see just how far this can be pushed, all you need to do is look at the current record-breaking fasting time. It clocks in at an amazing 382 days. 

This is what prolonged fasting is. It’s a major calorie restriction that lasts at least two days. In many cases, prolonged forms of fasting will last from two to five days. However, some people go as far as fasting for a couple of weeks while consuming only plain tea, black coffee, and water. 

For those who are beginners to fasting, prolonged forms are not recommended. Intermittent fasting is easier to get used to. If you want to try prolonged fasting after you have some experience with the intermittent version, that’s an option. Your body will be used to the process of ketosis and you’ll experience fewer problems. 

For instance, you might start with a 14:10 fast and slowly move to a 24-hour fast before transitioning to one that lasts two days and so on. 

Intermittent Fasting

Intermittent fasting is the other common form of fasting. It also happens to be very popular right now. It requires less prep and commitment than going on a prolonged fast. Instead of not eating for several days, you would fast and eat during certain hours. This makes it a process that you can potentially do on an indefinite basis.

This isn’t the same as a traditional diet since there are fewer restrictions on what you eat when you are not fasting. There are a variety of intermittent fasting options, such as one-meal-a-day fasts, alternate-day fasts, and 5:2 fasts.

Time-restricted eating is another form of intermittent fasting where you fast part of the day and have time to eat the rest. These include 12:12, 14:10, 16:8, and even 20:4 fasts. Everyone practices this in their daily life to some extent. It’s just planned and put into place during certain hours to count as a true fast. 

Before You Get Started…

There is one guideline we’d like to share before you decide to move forward and try fasting. It’s very important that you speak with your primary care physician before you move forward and take this journey. 

Learning to fast can be a challenge even if it’s common among those you know. If you’re the first person in your circle to try fasting, it may be even more difficult. You need to be sure you start slowly and ensure you’re eating a healthy balanced diet before you begin the fasting process.

For instance, if your diet is full of carbohydrates and sugar, fasting can make you feel unwell. It can also lead you to binge eating. Working with your metabolism would be the first step, in this case, to make sure you remain satiated and have the proper nutrients when you are fasting.

Moving to a diet that has no processed foods can be a good start. Try eating more protein, vegetables and fruits, healthy fats, and whole grains (but only in small amounts). Once your doctor agrees your nutritional deficiencies and metabolic and hormonal imbalances have been taken care of, you can move on to fasting.

As with other lifestyle changes, fasting might work well for one person but not the next. This is why it's essential to be sure you've spoken with your doctor before you make this, or any other major dietary change.

Some chronic conditions and medications may not be appropriate with fasting. In addition, people who are breastfeeding or pregnant should not fast for long periods. An individual with a nutrient deficiency should also typically eat at least once every few hours.

Having low blood sugar is a consequence of fasting. However, this may trigger migraines in some people. This marks another reason you need to speak with a physician before you begin fasting.

If you take diabetic medications, including insulin, you want to speak with a doctor before taking part in any form of restrictive caloric intake, including fasting. Fasting may be possible, but your blood glucose levels will need to be monitored and your medications adjusted to avoid hypoglycemia. If you do become hypoglycemic, it may cause you to feel lightheaded, confused, sweaty, shaky, and dizzy.

Research about fasting indicates that each person may respond differently to it. Your doctor can help you personalize how you fast so it’s suitable for your needs. 

Before you take part in your first fasting experience, you need to speak with your doctor first. Make sure it’s safe for you and something you can take part in with little to no risk.