The topic of fasting frequently generates some questions or comments ranging from the obvious “Why do you do that?” to “Not eating for so long is unhealthy, isn’t it?”. Here I would like to share with you the various forms of fasting and what some of the benefits are. Please however note that the content presented is for informational or educational purposes only, and does not substitute any professional medical advice or consultations with healthcare professionals.

So, what is fasting? Simply put, it is an extended period of time where you do not consume any calories whatsoever – not from food and also not from liquids, however water, certain teas and black coffee is allowed. The simplest form of fasting is called intermittent fasting, where you divide a 24hr period up into an eating window (where you do consume calories) and a fasting window (where you do not). The fasting window can range anything from 16 hours to 23 hours.

You also have other forms, such as alternate day fasting (eating one day, fasting the other), and the 5:2 split where five days of the week are normal eating days, while the other two restrict calories to 500–600calories per day.

Longer fasts, typically lasting more than 24 hours, as you would expect, means that you go for much longer periods without consuming any calories.

To understand what the benefits of fasting are, we need to briefly look at what happens when we do eat, and then what happens when we do not eat.

Whenever we eat or drink something that contains any of the macronutrients (fat, protein or carbohydrates), the content are broken down through the process of digestion into their most simplest forms (fat is broken down into what’s called glycerol and fatty acids; protein into amino acids and carbohydrates into glucose, also more commonly known as sugar).

We need these various building blocks (glucose, amino acids, glycerol and fatty acids) for energy, to heal, repair and build new cells and tissues in our body. Upon absorption these nutrients enter our blood stream and stimulates our pancreas to release a hormone called insulin. Glucose, or sugar, has the largest stimulatory effect on the release of insulin, which allows for glucose to enter our cells and to be used as a source of energy. This way, insulin ensures that the rapid rise of blood glucose levels (called hyperglycaemia) gets lowered again towards a narrowly regulated level. 

Now take a moment to reflect your own eating habits during a typical day. You may have been told that breakfast is the most important meal of the day, or perhaps you skip it to later snack on something, then eat lunch, and supper while snacking in between and afterwards. Considering the average intake of carbohydrates in the Netherlands is 230 grams per day [1], (which most likely consist of things such as cereals, bread and sugary drinks), every time you eat, and particularly when eating a diet rich in processed carbohydrates, you stimulate the release of insulin to remove the glucose from your blood steam and store it in cells. Whenever we consume too much glucose, it gets stored in our liver, muscle and eventually in fat cells, as reserves.

Excessive stimulation of insulin can have negative consequences for the pancreas (it can lead to burnout of the cells producing insulin, which means that the pancreas cannot create enough insulin to accommodate the frequent rise of blood glucose levels) but also that the cells in our body no longer effectively respond to insulin – something called insulin resistance. Both these scenarios – too much glucose in our blood and a resistance to insulin has been associated with many diseases of modern lifestyles, such as high blood pressure, coronary artery disease, obesity, chronic inflammation and type 2 diabetes.

One of the benefits therefore of going longer periods of time without eating is that you end up restoring the sensitivity of your cells to insulin, to have the cells of the pancreas rest and recover from having to produce too much insulin, too often, and to have less frequent and excessive fluctuations in your blood sugar levels. Studies have shown that intermittent fasting can have beneficial effects on insulin resistance, blood pressure and diabetes. [2,3] 

I mentioned earlier that one of the functions of insulin is to store excess glucose in our liver, muscles and fat cells. For the majority of our existence we as humans naturally experienced periods of famine, and intermittent periods where we had food to eat. Therefore we needed some type of energy storage mechanism during periods where food was abundant, but also one which we could transport around with us as we moved about. Remember, this was before the times of fridges or thuisbezorgd where you had 24/7 access to food.

If we therefore pay particular attention to where fat gets deposited on the body (around the abdominal area, waist and upper thighs), it’s actually another example of the intelligence of our body, to store it in areas where it does not impede our movement (I.e. it’s not around our lower legs, or upper back, but around our center of gravity) and this can be likened to a fanny pack which we carry around us to have on the go access to energy during periods of famine.

Furthermore, you may or may not be aware of this, but our body used to be very efficient at using fat as a fuel source – not only sugar. But a problem with frequently eating and consuming calories is that our body never gets to use its own stored reserves of glucose, therefore just adding to the fanny pack, but not really taking anything out. What makes this even more problematic, is that chronically high levels of insulin actually blocks processes where our body would naturally break down stored fat to be used as energy. Prolonged fasting forces the body to start using up its own energy reserves (for example in the liver) and eventually, once insulin resistance is no longer a problem, to start using fat, particularly in the form of what’s called ketones, as fuel for energy.

Therefore one of the added benefits of intermittent fasting is the loss of weight – not necessarily due to restricting the amount of calories you eat, but by restoring the natural metabolic flexibility our bodies used to have, to use both fat and sugar as energy sources.

But, the benefits of fasting extends beyond weight loss, since most people tend to make the assumption that when you do not eat, you consume less calories, and you will lose weight. While this is indeed true, losing weight is the end result of restoring normal metabolism and hormonal regulation within the body, and reduces your risk of developing lifestyle diseases such as heart disease or diabetes. But what other benefits does it deliver?

When we go for longer periods of time without food, and now I’m talking about longer than 24hrs, naturally we are not getting the three building blocks (amino acids, glucose and fatty acids) from outside in the form of food. This therefore forces the body to start looking at internal sources to generate these nutrients.

After fasting 16-18 hours or longer, and once the glucose which were stored in your liver is depleted, the liver starts to breaks down fat to make a substance known as ketones – a natural source of fuel in the absence of glucose reserves. Ketones are actually a very good source of energy for the heart, muscles, kidneys and also the brain. Using ketones as a preferred fuel source can actually heal the body, generate more energy, and help your body burn energy in a cleaner way.

Probably one of the most beneficial effects of prolonged fasting (that means 36hrs or longer) is what’s called autophagy, which literally means “to eat oneself”. Now I know that in itself would send alarm bells ringing, but this process is actually incredibly intelligent and beneficial to our cells. Autophagy is a natural process where the body starts recycling unnecessary, old or damaged components found within our body – this can be from our own cells, or foreign cells such as cancer, viruses or bacteria. With these prolonged fasts, our body is forced to slow down certain unnecessary processes and to look for alternative sources of building blocks within the body. It starts identifying old and dysfunctional cells and tissues, and recycles them into new cells or parts of cells. This process provides us a crucial defense mechanism against cancer and infections and also can protect our brain against neurodegenerative diseases (such as Alzheimers and Parkinson’s disease) [4]. I don’t know about you, but these are some significant health benefits, simply by not eating.

Other benefits of prolonged fasting, which is beyond the scope of this video, but certainly worth mentioning in brief include:

• Increased levels of what’s called BDNF (Brain Derived Neurotrophic Factor) which play a huge role in how well we age, and how well we learn and perform mentally.

 

• Increased levels in human growth hormone which helps to maintain, build, and repair healthy tissue in for example the brain and in muscles. It can boost your metabolism, and help you burn fat. One study found that after a 3-day fast, your HGH levels increase by more than 300%.

 

• And lastly it is beneficial to the gut biome allowing the good bacteria to flourish, through improving and stabilising the immune system in our gut, our first line of defence against pathogens.

 

So I hope this was informative and insightful as to the potential benefits of fasting, even if simply may mean to skip your breakfast and to time your eating for example between a 6-8 hour period. This is not meant to be an exhaustive overview of fasting, since there’s much more to the topic than simply not eating.

 

[1] https://www.rivm.nl/bibliotheek/rapporten/2020-0083.pdf

[2] https://www.sciencedirect.com/science/article/pii/S1550413118302535

[3] https://pubmed.ncbi.nlm.nih.gov/33531076/

[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3106288/