What is fasting and what are its advantages and disadvantages?
One of the hottest topics in the fitness world is certainly fasting. Just as every two or three years a certain way of eating or a supposedly miraculous diet is massively popularized, so is in the past 5 years the term fasting, i.e. refraining from consuming food and certain drinks, has become popularized little by little, all for the purpose of improving the body’s health functions or losing weight
My first encounter with the idea and term of fasting happened during my stay in Bali, when I dared to fast for the first time and try out what exactly it is about. At first, I thought only one thing, and that was that I would die of hunger – but something completely opposite happened. And that’s why today I’m writing about this topic that interests and intrigues many people and maybe who would like to experience it themselves, but they are afraid or have prejudices, just like I had them.
While many today associate fasting exclusively with the trend of so-called ‘intermittent fasting’, actually fasting itself has been known to people for thousands of years as an excellent way to ‘reset’ the body. As we know, fasting can be done for health, ritual, religious or ethical reasons, but today we will concentrate only on health reasons – and in a concise form I will help you learn something new about fasting and all its shortcomings and benefits, as well as share with you my fasting experience.
First and foremost – why do we fast?
Fasting has been used for therapeutic purposes since at least the 5th century BC, when the Greek physician Hippocrates recommended abstinence from food and drink for patients who showed certain symptoms of illness. Some doctors have recognized the starvation instinct, whereby patients in certain disease states naturally experience a loss of appetite. Thus, doctors felt that giving food during such conditions was unnecessary and perhaps even harmful, as fasting was considered an important natural part of the recovery process.
Until the 21st century, fasting was so often prescribed for the treatment of certain chronic diseases, but in fact there were no clear studies that would directly show that fasting is crucial for the recovery of patients. Today, however, we know that when it comes to fasting, there are two sides of the coin – one that can cause unpleasant side effects if fasting is not carried out in optimal conditions on a healthy person, and one that can greatly improve our health picture.
My personal experience is, of course, only mine, but I can say that it is extremely positive and I will describe it to you in detail. It is important to emphasize that each of us is an individual who reacts specifically and differently to such ‘experiments’, so if you decide to fast like me, you do not necessarily have to experience the same side effects and sensations.
My fasting experience
Let’s start with the story of my fast – and it starts from the time of my childhood. So, I was exposed to periods of fasting from an early age, although I may not have known it. I have always belonged to those people whose eating window is relatively short, i.e. the time when I don’t eat is relatively long. For me, that average since childhood meant roughly 15/16 hours of not eating and 9/8 hours of eating. I believe that it is due to the fact that I started dancing classical ballet at the age of 5 and it did not suit me at all to do ballet on a full stomach, so the morning fast, plus not eating in the evening during performances, turned into a lifestyle. Of course, in those years I didn’t know about the concept of fasting as we are talking about today, so I became familiar with it last year and decided to systematize my annual average fasting and it turned out that it was 15.4 hours as the time during the day in which I do not consume food. I must admit that I was surprised because I thought it was no longer than 14 hours. This is key information about my previous habit of not eating windows – so I wasn’t even aware of it, and I was already fasting practically every day.
I tried my first real longer fast in 2019, and that was immediately 36 hours without food while I was in Bali. I was surprised that it wasn’t as difficult as I thought. It was actually fantastic! I wasn’t hungry or tired, and on the day of breaking the fast, when I had already fasted for 30+ hours, I had such an amount of energy that it was simply unbelievable. I experimented with these longer fasts until 2022, when due to increased stress while working on the &Body online program project, triggers related to my ballet-induced eating disorders appeared. I decided to stop fasting for as long as it takes until I regain full control and re-establish healthy relationship with food – this happened recently, when I fasted again for 40 hours after a long break.
So, I ended that almost year-long break two weeks ago because I felt ready for it both mentally and physically. It was really a great 40-hour fast, and last week I tried the 38-hour fast again. I will repeat it again soon because I am collecting data on Garmin and Oura ring because I am interested in personal statistics related to the processes that accompany fasting.
What I have noticed in these two recent posts is the expected drop in heart rate, reduced heart variability and lowered body temperature. You can see everything in the attached statistics and pictures. Of course, these are only two posts, but the information is almost identical. When I gather at least 10 fasts in a row, I believe that I will dedicate one blog post only to that.
I will say right away that not every fast is the same and that there are different methods and ways of fasting. Personally, I start my fasts in the evening after dinner. In particular, as Thursdays are my rest day, I chose that day for fasting. I started fasting around 6 pm and broke it with a light meal on Saturday around 10 am. It is quite important that the first meal is not heavy and large, because the body does not need an initial shock of heavy food, and believe me, you will not even feel need to overeat.
How to fast and what types of fasting are there?
As we know, today it has been scientifically proven that fasting has numerous beneficial effects on the body, and in recent years it has become popular all over the world, but many still do not know that there are differences in the types of fasting. It is important to say that fasting, although it may seem impossible, can fit into everyone’s lifestyle, and there is no reason not to fast sometimes in a way that is acceptable to you.
The two most common ways of fasting are long-term fasting, which usually lasts more than 24 hours, and TRF, or time restricted eating fasting, which is actually a form of intermittent fasting, currently the most popular fasting option in the world. Here it is very important to indicate that TRF and intermittent fasting are not synonymous and that there are differences between them.
TRF – Time restricted feeding – TRF is a form of fasting that includes changes in eating and fasting, so a person consumes food in certain periods, and only drinks in certain periods. Thus, most people who use this method of fasting eat in a period of time lasting a maximum of 8 hours during the day, while the rest of the hours are fasted, i.e. they refrain from eating. In fact, it is a feeding pattern that divides the day into night and day, that is, the time when we do not eat and when we eat. Currently, studies of the effects of this type of fasting mostly refer to research conducted on animals and the effects of such fasting on their bodies, so scientists still have to prove and explain the effect of TRF on human longevity and aging of the human organism.
Intermittent fasting – Intermittent fasting is currently the most popular form of fasting, and it can be done in different ways, which is why it is so attractive to the general population. Namely, you can eat during a certain period of time during the day, while fasting the rest of the day, or else you can limit your food intake to one meal a day, while the rest of the time you only drink liquids – for example, two days a week. The essence of fasting is to signal the body to start burning fat in the body, and not the calories that we only recently consumed with the last meal. Longer periods without food trigger our body to reach for ‘fat stores’ and thus speed up the work of our metabolism, help with weight loss and give us a feeling of new vigor and energy. Ultimately, intermittent fasting can help create metabolic flexibility and the ability of the body to draw energy not only from glucose but from fat, and that at the cellular level. TRF is actually a form of intermittent fasting.
Long fast – A long fast is considered abstinence from food for a duration of more than 24 hours, and it can be extended from one day to a week or more – depending on the health of the individual, goals and mental and physical readiness. Although a long fast is considered a very favorable way to ‘reset’ the body, before carrying it out it is necessary to consult a doctor and see if there are conditions or diseases for which you should not fast. For example, it is not recommended to fast for people with diabetes because it can lead to wild blood sugar levels, which can be life-threatening for diabetics.
In general, if you are going to fast, you should know that fasting is not recommended for people who are underweight, teenagers and the elderly. However, if you decide to fast, below are the guidelines that I follow myself to make it easier for me to fast, as well as the general recommendations of doctors and nutritionists on this topic. If you follow them, I am sure that you will get the best out of fasting for yourself and your body.
Tips & Tricks on how to fast:
To begin with, I will start with myself and list the following methods that I practice in order to make my fasting enjoyable and successful.
I consume increased amounts of calorie-free liquids. These are: water, teas (not fruit), coffee and mineral water.
I don’t eat food or any other calories.
I don’t train for the first 36 hours (all Friday), but I walk, stretch and do mobility exercises.
In the morning, when I break my fast, I train. Preferably strength training or shorter cardio, and sometimes both. I definitely have an increased energy level, so I take advantage of that.
After training, I eat my first meal, which is always smaller, lighter in protein, but with carbohydrates and fats.
I continue to eat as regularly as any other day nutritionally rich meals and do not make up for food from the previous day. I would especially emphasize that it is a counterproductive mindset to eat the so-called ‘cheat meal’ because you haven’t eaten so now you can stuff yourself! Namely, we fast in order to provide and give the body something good, so feeding it ultra-processed food with added sugars is really harming to the newly renewed metabolism.
On fasting days, I try to occupy myself by reading books, listening to podcasts or participating in social activities, but with friends and close people.
I avoid events with large amounts of food as well as crowds in general. They increase stress which can increase anxiety and fatigue.
I choose a day for fasting when I do not expect to be under increased stress.
• If I feel tired, I do NSDR, meditation, breathing exercises or take a nap. It doesn’t happen to me, but if you’re feeling lethargic or tired I’d definitely recommend it.
• To everyone who would try it, I want to say first that they should not think about what they lose (food), but what they gain. That is, what is given to the body by fasting – time to restore and perform all those processes that are slowed down. Fasting also gives us an easier knowledge of how much food we don’t need in the quantities in which we consume it in modern society – we eat only because food is easily available. Also, fasting gives mental clarity and physical lightness and this is something that you could fall in love with at the first moment, so it is not uncommon for those who try a longer fast to start practicing it several times a year.
My recommendation would be that you don’t do it more often than every few months because you risk losing muscle mass, and as I’ve already mentioned countless times – muscles need to be protected and built because they are the fountain of your youth.
The general instructions are that if you have decided to try fasting, make sure you are well hydrated all the time and that you are taking in sufficient amounts of liquid. If you use the TRF or intermittent fasting method, pay attention to the fact that during your meal time you take in an adequate amount of calories and nutritionally rich food that will satisfy your body’s needs for all micro and macronutrients.
During a long fast, it is recommended to refrain from heavy physical activities and indulge in rest, and the general recommendation is to fast only during periods when you do not have an elevated level of stress. For example, it is also good for women to know that they should not fast just before the start of menstruation, as this will lead to additional hormonal imbalances and feelings of weakness and lethargy.
If you want to fast for a day or two and abstain from food during that period, an excellent method is to start your fast after dinner on the first day and to fast until breakfast on the third day or evening on the third day, which would allow you to fast for 48 hours.
Despite the popular belief that one should not drink coffee or tea during fasting, these drinks are allowed for consumption as long as they do not contain milk, cream or sugar – that is, calories. The most important thing is to prepare mentally that you may experience a lack of energy, fatigue and a slight headache on the first day, but it is more about a psychologically conditioned reaction to the lack of meals than the actual hunger of the body. In any case, the key point when fasting is to pay attention to fluid intake, because the biggest danger with a long fast is dehydration.
What happens to the body during fasting hours?
So, already in the first 4 to 8 hours of fasting, our blood pressure is lowered and insulin levels in the blood stabilize and become lower. Within 12 hours, the body has digested all the food that we consumed in the past day, the digestive tract goes into a state of rest, and the healing processes of inflammatory processes in the body begin. After 14 hours, the body begins to use energy from fat stores and caloric consumption from fats increases, and already after 16 hours of fasting, research shows an additional ‘momentum’ in the consumption of fat stores. During 20 hours of fasting, the process of autophagy starts, i.e. the organism’s self-preservation mechanism through which the body removes non-functional, damaged and diseased cells and acts in this way to recycle cells and cleanse the body of toxins. If you manage to fast for 36 hours, autophagy will increase by 300 percent – which works wonders on the cellular level of your body. After 48 hours of fasting, cell regeneration begins and a reduction in inflammatory processes in the body can already be noticed.
In the following, I will list and explain the health benefits, as well as the possible complications of fasting – so that you know exactly what to expect and what to watch out for.
Health advantages and disadvantages of fasting
Health complications often attributed to excessive fasting include electrolyte imbalance, thinning of the hair, but also potentially fatal heart arrhythmia and kidney failure. It is recommended that you consult a doctor before long-term fasting, and there are also individuals who should not fast at all. These are people with type 1 diabetes, people with low blood pressure, people with a history of eating disorders or people who are too thin. Also, fasting is not recommended for pregnant women, lactating women, women who want to conceive and people with anemia. Thrombophiliacs and hemophiliacs who take blood medications are also not among the people who should fast.
However, there are many more positive effects than the chances of something seriously harmful happening to you from fasting. As things stand, research shows that limited food intake and intermittent fasting have beneficial health effects, including reduced risk of cancer, heart disease, immune disorders, diabetes, and slow aging and have a beneficial effect on longevity. A number of studies point to a favorable influence on the success of chemotherapy implementation.
What is important to note is that fasting is defined as short-term or long-term abstinence from food (primary), and can last from 8 hours to several weeks. It is very important that people who are fasting are informed about all the side effects of fasting and that they know how to properly react to the changes that will happen in their body, which they will definitely feel.
Studies also show that a 48-hour fast has a positive effect on weight loss, the body’s sensitivity to insulin, and reduces inflammatory processes in the body, which leads to an extension of the ‘shelf life’ of our body’s cells and longevity.
As for the medically proven benefits of fasting, studies have shown that intermittent fasting, i.e. intermittent fasting for a period of 8 to 12 weeks, can lead to a reduced concentration of LDL cholesterol (20-25%) and triacylglycerol concentration (15-30%) in the blood. Similarly, statistics show that individuals who fast for at least 24 hours (once every two weeks), over a 12-week observation period, reduce their total cholesterol by 10 to 12 percent.
Also, the latest studies show that intermittent fasting is very important for people who want to lose weight or change the way their metabolism works. Namely, the results of an all-day fasting experiment lasting 12 to 24 weeks show an improvement in blood lipids (5%-20% reduction in total cholesterol and 17%-50% reduction in triglycerides). The results of the aforementioned studies together suggest that fasting can reduce lipids in the blood, which in turn means that the body consequently begins to consume fat in the body in a different way. The switch from preferential lipid synthesis and storage to fat mobilization usually occurs when glycogen in hepatocytes is depleted (12-36 hours after the onset of starvation) and the rate of lipolysis in adipose tissue increases and causes increased levels of plasma free fatty acids (FFA) to production of increased ketones derived from fatty acids in the liver, kidneys, astrocytes and enterocytes as a source of energy.
Also, during fasting body has an opportunity to release energy in the form of heat, which ultimately increases energy consumption and thus leads to the consumption of more calories. Scientific and medical studies also show that fasting can significantly change our state of health, especially regulating blood glucose. Namely, measurements after an 8-week intermittent fasting regime show that the glucose of obese adults decreased significantly, and the insulin levels of the study participants also decreased, although not significantly. It also shows that people who fast for approximately 48 hours once every two months have more stable glucose levels, which is especially important for people with type 2 diabetes.
Psychological effects of fasting on people
However, in addition to numerous benefits, there is often talk about the negative impact of fasting on an individual’s psychological state. Some studies have reported that short-term fasting can increase negative emotions (depression, anxiety, anger, irritability, fatigue, and tension) and decrease positive emotions and vitality. In studies on consecutive short fasting, subjects’ lower positive mood, stronger negative mood and lower perceived work performance were observed, but longer fasting according to research leads to a sudden surge of energy, a feeling of ‘lightness’ and mental clarity. In this context, scientists often note that it is about individual measurements of the subjective impression of individuals, so it is difficult to say exactly how fasting universally affects people – it is more about a subjective emotional impression that depends on many external factors.
What is certain and what psychiatrists agree on is that fasting is easier to maintain if we are not under a lot of stress, if we are rested and do not participate in heavy physical work or activities. Staying in daylight, adequate hydration and ‘distraction’ during the day are recommended, so that we don’t focus only on the fact that we feel hungry and don’t eat.
So, if you decide to follow in my footsteps, as well as in the footsteps of thousands of people around the world, and try intermittent or long fasting, be sure to take these tips and advice into account and mentally prepare yourself for a little discomfort- which will in longterm bring numerous benefits for your mind and for your body.
Effectiveness of an intermittent fasting diet versus continuous energy restriction on anthropometric measurements, body composition and lipid profile in overweight and obese adults: a meta-analysis – https://pubmed.ncbi.nlm.nih.gov/33293678/