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The Scientific Effects of Fasting on the Body

Fasting is the practice of abstaining from eating food or drinking liquids for a set period of time. It is a powerful tool that today is still widely misunderstood as dangerous, extreme, or simply regarded as a diet fad to lose weight. Despite this, fasting is an amazing mechanism that we can use for healing the body from the inside out, facilitating cellular repair, and even goes hand in hand with deep spiritual practices.

Plate Fasting

When we eat food, our bodies have to spend energy breaking down and digesting the meal. Depending on the type and quality of food, such as heavy meats or incredibly processed snacks, it can take even more energy for your body to turn that food into the various nutrients that your body then uses for fuel.

However, this means that when our bodies are busy digesting, there is significantly less energy spent on the multitude of other processes and functions that the body normally does, such as cellular repair, turning excess fat into energy, and fighting off disease.

Fasting then (at least on a physical level), allows the body to relax the digestive system and apply 100% of its energy to the rest of the body where needed.

The benefits of fasting are a rather long list of physical benefits, from helping our brains ward off neurological diseases like Alzheimer’s and Parkinson’s, to inducing cellular repair processes, lowering the risk of diabetes, reducing stress and inflammation and even preventing cancer.


How Fasting Affects The Brain

Brain FastingWhen we eat, glucose is stored in our liver as a form of fuel called glycogen. This takes up to 10 – 12 hours to become depleted from our system. Once it’s all used up, our body starts burning fats which are converted into ketones, a natural chemical that our brains use for energy.

Ketones play a vital role in shifting the structure of our neural synapses to promote heightened learning and improve our overall brain health. However, when we are constantly introducing new food into our system, our bodies don’t have the chance to deplete the glycogen in our liver and, thus, ketones aren’t able to be produced.

Mark Mattson, a professor of Neuroscience at the John Hopkins School of Medicine has conducted numerous studies showing the benefits of intermittent fasting.

His experiments showed that limiting your caloric intake for two days a week can drastically improve neural connections in the hippocampus – a part of the brain which regulates long and short term memories.


How Fasting Repairs Cells

In the BBC documentary Eat, Fast & Live Longer, television journalist Michael Mosley sets out to experience the benefits of fasting himself. One of the most prominent factors he learns about is the growth hormone called IGF-1. This stands for insulin-like growth factor. It is a hormone within us that keeps us in “go” mode, and is important for when we are children growing up, allowing us to grow taller and increase our body sizes where necessary.

Cells FastingHowever, later in life we don’t need to grow so big, and normally IGF-1 levels drop significantly. If the levels are too high, they are often responsible for fuelling tumor growth and other forms of cancer or disease. When the IGF-1 hormone levels are too high, are bodies are kept in a state of growth mode, rather than repair mode. These IGF-1 levels can raise beyond normal levels when we eat animal foods, as many studies have found high IGF-1 levels linked to proteins from milk, seafood, red and white meat, and other foods with high amounts of saturated fat.

To reduce IGF-1 levels, there are several actions we can take. Besides omitting these types of foods from our diet, studies have also found that we can rapidly reduce IGF-1 levels to a normal state with a short 3-day water fast. Upon these levels dropping, a number of repair genes are activated, and begin to heal the body from the inside.

You can watch Michael’s entire journey and transformation here.

A scientist named Valter Longo, featured in the BBC documentary above, is a Gerontological researcher at The University of Southern California. He and his colleagues have shown that fasting eases side effects of chemotherapy, and promotes health advantages to the body. His team found that reducing the amount of food in middle aged mice for two 4-day periods each month actually allowed those mice to outlive their peers by about 3 months.

They also saw that those mice were 45% less likely to develop cancer and their insulin levels were 90% lower. These mice were still able to retain their mental ability and beat the control animals in two kinds of memory tests.

In another study, short term fasting was as effective as chemotherapeutic agents in delaying the progression of tumors in mice. This study concluded “That multiple cycles of fasting promote differential stress sensitization in a wide range of tumors and could potentially replace or augment the efficacy of certain chemotherapy drugs in the treatment of various cancers.


The Difference Between Fasting and Eating Less

Here is a great video that explores the difference of when you reduce your caloric intake, versus cutting out food entirely.

In 1944, a study called the Minnesota Starvation Experiment was conducted to see the effects of caloric restriction due to the amount of people suffering from starvation as a result of the ongoing World War and to see what kind of aid should be provided to as a relief effort. The physical and psychological conditions of the men were extreme, from being very cold to completely obsessing about food. They only thought about food and exhibited neurotic behaviors like hoarding cookbooks, and even eating rotten vegetables out of desperation.

Water Bottle FastingDr. Jason Fund, a Toronto physician explains that reducing your caloric intake actually results in more difficulty losing weight, making it easier to lose more lean muscle mass. Those who do this are generally in a constant state of hunger. However while fasting, you are only hungry for the first few days during peak periods (usually the times when you normally have breakfast, lunch, and dinner), before the sensation completely disappears and your energy levels stabilize.

This is due to the amount of Ghrelin in the body. Ghrelin, also known as the hunger hormone is responsible for the feeling of hunger and weight gain. Generally, ghrelin levels spike in the morning, at lunch, then dinner time because our bodies have been programmed to expect food at that time. A study conducted at Aarhus University Hospital in Denmark found that in the first 84 hours of fasting,ghrelin levels continually decreased. Typically after the first 3 days, hunger disappears altogether.

Water Bottle Fasting 2What also happens after the first several days is that our bodies goes into a state called ketosis. This is one of the most important factors in fasting. Ketosis is when your metabolism switches to using mostly fat for energy, rather than carbohydrates and glucose.

This is why the subjects in the Minnesota experiment had very little energy and found themselves becoming very sluggish. They were eating just enough to keep their bodies out of ketosis, so they were unable to use their body fat for energy. When you restrict calories, your insulin levels drop drastically and your metabolism slows down, leaving you feeling tired and hungry.

On the other hand, when you cut out food entirely, your metabolism actually speeds up, and allows you to maintain a normal level of energy in your body!


Different Approaches to Fasting

Fasting can be an amazing practice, however for many it can be difficult to get started. Mark Mattson recommends trying one of two possible ways to begin fasting that’s gentle for most people who want to give it a try. The first system is called the 5:2 diet, which limits your caloric intake to 500 calories, two days a week.

We typically eat around 2,000 calories a day, so this is a substantial reduction. This would equate to 1000 calories a week, but splitting it up into two meals gives your body time inbetween to reach ketosis. As opposed to splitting it up daily and eating 145 calories or so a day, which as we discussed above would result in exhaustion and much more hunger pains.

Drinking water fastingThe other way is what we’re calling “window eating”, which is the purposeful timing of your meals so that you eat in an eight hour window of time, giving your body enough time to exhaust its levels of glycogen and start producing ketones. You can extend this practice a bit longer, and give yourself a small window of time to eat every day, reducing your daily meal count from 3+ meals to 1 meal over several hours, and then fasting roughly between 18 to 22 hours every day.

This was discussed in this video, and the amazing benefits of doing so. However, as our bodies take anywhere from two to seven days to get fully into a state of ketosis, this practice may still result in feeling sluggish or being really hungry still. There is also the remarkable dietary practice of the people of the Okinawa island in Japan. The people here have some of the highest longevity rates in the world, with women expected to live up to an average of 90 years old.

They call this diet the Hara Hachi Bu, a practice of eating until you’re only 80% full and then stopping. This has been shown to reduce cardiovascular risks, diabetes, help with weight loss and increase longevity. There are many different types of fasts, from strict water fasts, juice fasts, general liquid fasts with teas and tinctures, the Ramadan fast, or even dry fasting which is no liquid or food at all.

Dry fasting is a sort of “next level” fast, for those who wish to do a deep cellular cleanse on the body, but not for the faint of heart or those new to fasting. If you’d like to learn about dry fasting, you can read about them here! Ultimately, you know how your body feels better than anyone else, and it’s important to tap into your physical being and listen to how you feel. An extended fast might be beneficial to someone, while shorter, intermittent fasts may benefit someone else depending on their body type and state of being.

If you are interested in fasting and it’s your first time, start slow! Try a 12 to 24 hour fast, and see how you feel throughout the day. If you want to challenge yourself, a great starting point is simply fasting for 1 day a week. You may find it difficult at first as hunger sets in and our moods shift, but the more you practice it, the more you see how much of these sensations stem from our mentality, rather than our physicality.

We made an Everyday Magical Things episode on Fasting which covers much of this information which you can watch here!


The Root Chakra and Fasting

The main aspect that closes our root chakra is fear, predominantly fear for our survival, and there is quite a large fear surrounding fasting for many people. We may have an innate belief that if we don’t eat 2,000 calories in a day, that we might be extremely weak and this fear can prevent us from learning and experiencing the fullest extent of what our bodies are really capable of!

Pouring water fastingWhen we have faith in our bodies we are capable of healing ourselves and fasting can truly aid in that journey by testing the waters of what our bodies can really do! We must have faith in ourselves and the inherent ability we all hold to repair our bodies on a cellular level.

If you have never gone on a fast before and are feeling fearful of your own ability to go without food for several days, take a few deep breaths and know that your body is stronger and more able than you may give it credit for.

A huge part of fasting is holding a positive attitude and belief. Practicing deep breathing, meditation and staying in an uplifted state will allow your physical body to perform at levels beyond your wildest imagination!

If you’d like to learn more about the Spiritual aspects of fasting, click here to read our article about it!



Johns Hopkins Health Review

Fasting For A Longer Life

Fasting Cycles Reduce Cancer Cells

Short Term Fasting May Improve Health

10 Evidence-Based Health Benefits of Intermittent Fasting

The Power of Intermittent Fasting

The Science of Cleansing and Fasting Diets May Help Everyone

All about IGF-1

Igf-1 and foods that cause it to be too high:

101 Reasons to Fast


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8 Responses

  1. jimisimij says:

    Really cool article. Very informative. I’ve been looking into fasting lately. So how should you eat when you come off of a fast? Any particular guideline to follow the first few days following a long fast?

    • Spirit Studios says:

      Great question! When breaking our fasts we normally would start eating again with something like a raw green smoothie. It is easily digestible by our bodies and if you have green veggies in it you will get lots of easily accessible nutrients as well! Just remember not to over eat as this will stress your system and sticking to raw fruits and vegetables would be recommended! There is another good article here which gives some other insights as well 🙂

  2. Sapna says:

    Totally agree.. Amazing.. Great article.. Great work 👍👍👍

  3. Alana Gray says:

    Excellent. Me and my partner were only talking about fasting yesterday. Thank you for the insight and i love the chakra input to, very helpful. Keep up the great work. With thanks. Bless

  4. Veronica Sandu says:

    so…if I want to try fasting for one day per week, then two days per week and so on…should I drink water? (in those fasting days)

    • Spirit Science says:

      Yeah drinking water during a fast helps your body flush toxins and can help you feel full after drinking a large glass. Fasting without drinking water is called dry fasting and that is much more intense and we don’t recommend it unless you are seasoned with fasting and trust your own body enough to being dry fasting.

  5. Veronica Sandu says:

    Thank you for answering me and for all information! 🙂

  6. Victoria Rose says:

    This was an extremely helpful article! Thank you!!!

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