Fasting and Starvation

Today's text will not deal with popular diets like 8:16 or autophagy, but with starvation and fasting through the lens of evolution, culture, and science. I have already written about intermittent fasting and similar dietary regimens that include time-restricted eating, so if you want to read more about them go here: Intermittent Fasting.

Starvation simply means that we do not consume food for a longer period, while fasting is voluntary starvation, making these two terms very similar. For the purposes of this text, I will use both the word fasting and the word starvation to refer to a period during which no food is consumed at all.

The fact that fasting exists in almost all religions and all parts of the world indicates its significance. This is an exceptional mechanism and an acquired human capability rooted in our long history and biology. In Christianity, fasting is not only a physical but also a spiritual practice; in Islam, fasting during Ramadan unites the community and strengthens willpower; while in Hinduism and Buddhism, it symbolizes purification and discipline. In the world before modern religions, our ancestors, hunter-gatherers, frequently faced periods of scarcity, forcing them into involuntary fasting, which shaped the metabolism we have today.

Today, in a time of abundance and constant availability of food, starvation seems like an archaic and radical concept. I have encountered this many times in my practice, where the mere mention of not eating for 24 hours causes wide eyes and head-shaking accompanied by words like "Impossible!" or "A whole day?". Research and personal experiences tell us that fasting is not only exceptionally good for the body but also holds great value for the human spirit.

The question arises: why does fasting endure through the centuries? The answer lies in its numerous benefits, from regulating metabolism and cleansing the organism to mental peace and better focus. This text aims to provide you with a deeper understanding of this ancient practice, which is precisely what we need today.

The Evolution of Fasting

From the first traces of the human species to the modern era, eating habits have been shaped by the availability of food in the environment. Food was never as constantly available and abundant as it is today. Most of our ancestors relied on periods of abundance when they successfully hunted or gathered food, but they simultaneously went through periods of hunger, which were an inevitable part of life. An additional problem with hunger was its unpredictability; while it is possible to prepare for seasonal shortages, numerous causes triggered sudden scarcities. This unpredictability led to the development of metabolic mechanisms for unexpected periods of hunger, enabling human survival and adaptation in diverse ecosystems worldwide and causing humans today to live everywhere from the North to the South Pole.

Our understanding is that in the natural environment, the life cycles of all organisms, including humans, depend on resource availability. Natural cycles regulate nutrient availability through complex ecological interactions. The primary production of plants and the secondary production of herbivores control energy flows within ecosystems, while the final decomposition of organic matter is crucial for renewing nutrients and the soil so the cycle can begin anew.

What sets the human species apart from other mammals is an incredible capacity to adapt to a wide variety of foods, from a predominantly plant-based diet like that of people in tropical regions to a diet rich in fats and proteins in populations like the Inuit. This metabolic flexibility was crucial for survival, but it also meant the human body developed efficient mechanisms to maintain energy during prolonged periods without food.

Modern humans, us, are only the second or third generation of people who have the luxury of daily regular meals, making hunger foreign to us. However, through the long history of humans (about 200 thousand years), starvation was so common that people who didn't adapt well to hunger simply did not pass on their genes. For that reason, all humans living today are descendants of those who successfully adapted to periods of starvation, meaning every one of us possesses this incredible ability.

The Metabolism of Starvation

Our adaptation to periods of fasting can be proven by the existence of numerous changes in our body and metabolism during relatively short periods of starvation. One of the body's first responses to reduced energy intake is lowering energy expenditure and shifting to secondary energy sources. However, this process is far more complicated as the body further activates a series of hormonal and metabolic mechanisms to optimize the use of available resources, keeping the body capable of finding food for as long as possible.

When the body receives no food, a series of metabolic changes occurs to conserve energy and ensure the functioning of vital organs. In the initial hours of starvation, the body uses glucose from liver stores as its primary energy source. However, these reserves deplete quickly, in less than 24 hours, forcing the body to switch to alternative energy sources.

During prolonged starvation, two processes that are normally muted take center stage: gluconeogenesis and lipolysis, which represent the internal creation of sugar and the breakdown of fat stores. Gluconeogenesis enables the production of glucose from non-sugar sources, while lipolysis breaks down fatty acids in the liver to produce ketone bodies. Ketone bodies serve as an alternative energy source for the brain and other organs that cannot utilize fatty acids directly. This metabolic shift enables the activation of energy from "storage" and survival during an extended fast.

In addition to promoting fat burning, fasting also activates metabolic pathways associated with longevity. Studies on various organisms, from rodents to primates, indicate that caloric restriction can significantly extend lifespan, primarily by modifying signaling pathways. Although these effects in humans are still a subject of research, mounting evidence suggests that intermittent fasting can contribute to metabolic health and potentially slow down the aging process.

While it might seem from this that starvation is a good way to control weight or reduce body fat, one of the key phenomena in starvation adaptations is adaptive thermogenesis, which involves a reduction in the body's energy expenditure. During a rapid weight reduction, the body lowers the amount of energy it needs for proper functioning (basal metabolic rate), thereby counteracting further weight loss. Adaptive thermogenesis is the cause of plateaus during sudden weight loss, as well as the rapid regaining of weight after rigorous diets. This is one of the reasons why I am a strong opponent of restrictive diets. When a sharp reduction in food and weight loss occurs, mechanisms in our body slow down or halt to consume as little energy as possible. In this way, the opposite of the desired effect is achieved: people go on a diet to lose weight, and their body reduces expenditure so it doesn't lose weight, thus trapping them in a losing battle against their biology and their own body.

Fasting in Religion

Besides being a biological and evolutionary phenomenon, the practice of fasting is deeply rooted in practically all modern religions and numerous cultures worldwide. The reasons for fasting are always connected to spiritual purification, repentance, and discipline, but it is interesting to note that the value of fasting as a way to achieve a type of mental and physical reset is universally recognized.

Christian Fasting

In Christianity, fasting has a long tradition and is present in various forms. In Orthodoxy and Catholicism, fasting is strictly defined by church rules, while in Protestant traditions, fasting is a meaningful but individual choice. Fasting is viewed not just as a physical practice, but as a path to spiritual transformation and repentance. Jesus' forty-day fast in the desert, which is often taken as an example, highlights fasting as an act of temptation, but also of spiritual strength and endurance. According to text from the Serbian Orthodox Church, fasting is not merely physical abstinence, but a spiritual discipline that helps believers draw closer to God, free themselves from sin, and develop virtues like humility, patience, and love.

From a dietary perspective, Orthodox fasting involves abstaining from meat, dairy products, and eggs, which increases the intake of grains, fruits, beans, vegetables, and fish. With multi-day fasts and single-day fasts (Wednesdays and Fridays) observed by many believers, Orthodox fasting lasts between 180 and 200 days a year. This way of eating can be described as a periodic vegetarian diet, which, due to the presence of fish and seafood along with low meat intake, closely resembles the Mediterranean diet. You can read about the benefits of the Mediterranean diet in the POST dedicated solely to it, but the conclusion is that the Mediterranean diet is not only my favorite way of eating, but also one of the healthiest according to many studies and experts, making a diet that includes Orthodox fasts very good on paper.

While fasting in principle anticipates excellent effects on health and longevity, modern society has enabled fasting without sacrifice. In stores, you can find practically any product in its fasting (vegan) variant, such as: hard cheese, biscuits, chocolate, milk, meat substitutes... It seems to me that the spiritual act of fasting has been stripped of its meaning this way. However, for me as a nutrition counselor, it is far more critical that many of the positive health aspects of fasting have been completely lost. Clients who fast often consume an even greater number of highly processed items during the fast, along with large quantities of pastry, breads, and other flour products, resulting in a further deterioration of their already problematic diet instead of improvement. Therefore, the effects of Orthodox fasting on health vary personally, and there is no concrete conclusion on whether fasting is positive or negative for health.

Islam and Ramadan Fasting

One of the best-known and most structured forms of fasting in the world is the Ramadan fast, practiced by more than 1.8 billion people globally. The Ramadan fast is one of the five pillars of Islam and, besides food, includes abstaining from drinks and other behaviors (smoking, sex, excessive pleasure). During the month of Ramadan (29-30 days), believers practice fasting from sunrise to sunset, meaning the fasting hours during the day vary for different parts of the world.

Just like in Christianity, fasting in Islam is not merely physical abstinence but a method of self-control, gratitude, and spiritual discipline. Additionally, during Ramadan, believers make an effort to read the entire Quran and to understand and apply what they read in their daily lives.

Strictly from a nutritional standpoint, the Ramadan fast most closely resembles an intermittent fasting regimen, specifically 12:12 or alternate-day fasting. Most intermittent fasting regimens offer positive health benefits, which you can read more about in this text. A significant difference is that during the Ramadan fast, water intake is restricted alongside food. This restriction can cause health issues because ensuring adequate water intake during a normal day is already a challenge for most people, even when they can drink water all day long. Despite this, the Ramadan fast is proven safe for all healthy adult individuals, and groups of people whom it might negatively impact are exempt from the fasting obligation: children, postpartum women, the sick, those with arduous jobs, the elderly, and pregnant women.

The Daniel Fast

The Daniel Fast is a specific form of Christian fasting inspired by the biblical story of the prophet Daniel, who abstained from "king's food" and consumed only food of plant origin and water to remain faithful to his beliefs. Described in the Book of Daniel in the Old Testament, this fast is often interpreted as an example of discipline, spiritual devotion, and faithfulness to God.

The Daniel Fast is practiced mainly among Protestant groups as a way of spiritual renewal, abstinence, and devotion to prayer and faith. This biblical fast can last between 10 and 40 days, but 21 days of fasting is the most common practice. During the fast, believers abstain from food of animal origin, processed sugars, additives, preservatives, sweeteners, colorings, flavorings, caffeine, and alcohol—essentially all processed foods.

From a dietary perspective, this fast resembles a vegetarian variation of clean eating and brings significant health benefits. These positive effects are proven through a reduced risk of developing metabolic and cardiovascular diseases, as well as improving various blood parameters including LDL, LDL:HDL, glucose and insulin levels, HOMA-IR, blood pressure, and overall body weight. It should be mentioned that all studies on this type of fast were done on small groups of people and are significantly rarer compared to studies dealing with Ramadan and Orthodox fasting.

Jewish Yom Kippur Fast

Yom Kippur, known as the Day of Atonement, is the holiest day in Judaism and is marked by strict fasting and prayer. This holiday is observed on the tenth day of the month of Tishrei and represents the culmination of a period of introspection and repentance known as the Ten Days of Repentance.

The fast on the Day of Atonement lasts 25 hours and involves complete abstinence from food and drink, including water. Furthermore, believers abstain from other physical pleasures, such as bathing, using perfumes, and wearing leather shoes. As with other religious fasts, the goal of the fast, alongside physical abstinence, is a higher spiritual purpose through internal examination, seeking forgiveness, and spiritual purification.

From a nutritional standpoint, this fast is very intense but short-lived, so its effects cannot hold massive positive or negative significance for the body. It most closely resembles prolonged fasting regimens that can last from 24 to 72 hours. The difference in this religious fast is the water ban, which can have moderate negative health effects. I did not find papers examining the health effects of this specific fast, but we know that prolonged fasting has a positive effect, while a lack of water carries certain drawbacks.

Buddhist Fasting

Unlike the monotheistic religions discussed so far, fasting in Buddhism does not serve the purpose of prayer and repentance; instead, it is experienced as a means of personal discipline, purification, and enlightenment. Buddhists view fasting as a way to control desires, reduce attachment to the material world, and deeply understand the nature of suffering and impermanence. In some cases, Buddhists fast to develop compassion for those suffering from hunger, reminding themselves of the fleeting and unstable nature of physical needs.

Buddhist fasting can mean different things depending on the school of Buddhism and the region where people live. A common practice in Buddhism is lifelong vegetarianism, especially among monks, which adds another restriction to their diet alongside fasting. In Theravada Buddhism, monks practice fasting by not eating after noon, believing that this keeps their minds clear and their bodies unburdened. In the Mahayana tradition, certain Buddhist vows include specific fasting days, such as the eighth, fourteenth, and fifteenth days of the lunar month, when believers abstain from food, meat, and other pleasures. Vajrayana Buddhism features specific ritual fasts and is not necessarily vegetarian.

If we view Buddhist fasts strictly as dietary regimens, they all resemble various forms of intermittent fasting, which has been widely discussed. Studies mostly focus on examining the impact of a lifelong vegetarian diet rather than occasional short-term fasts. For example, a study conducted in 2009 examined the difference in body composition between Buddhist nuns who are vegetarians and Catholic nuns who are omnivores. They concluded that there were no major differences in the body composition of the nuns, though some moderate advantages of the vegetarian lifestyle were present.

Physical Effects of Fasting

A section on the physical effects of fasting was supposed to go here, but after a few days of research, I fell down a rabbit hole and wrote the following subheadings: Fat Metabolism; Sugar Metabolism; Protein Metabolism; Impact on Total Body Weight and BMI; Blood Pressure. This was not only massive, but truly exceptionally boring. Here is a brief summary of what I learned on this topic, but take everything with a grain of salt because many types of fasting and various measurements were used:

• Intermittent fasting can reduce visceral (bad) fat in the body.

• Fasting reduces HbA1c, a marker of blood sugar, making it good for people with prediabetes or metabolic syndrome.

• Fasting does not significantly reduce muscle mass, and when it does, growth hormone is secreted to accelerate muscle building after the fast.

• Fasting contributes to a reduction in body weight… Exactly how much? Well, it depends on the fast, but a solid number is 3% to 8% over a period of 3 to 24 weeks.

• Fasting improves body composition by reducing the fat percentage while preserving muscle mass.

• Fasting has a beneficial effect on blood pressure (especially in people with high blood pressure).

Psychological Effects of Fasting

Fasting has a complex impact on the psychological state of individuals, which depends on various factors, including the duration of the fast, individual inclinations, prior experiences, and the reasons why a person chooses to fast. For this very reason, it is impossible to give a definitive answer to whether fasting is good or bad. According to papers, short-term fasts, depending on numerous factors, can evoke both positive and negative emotions, while longer fasts generally follow a specific pattern of emotional changes.

An interesting study that tracked the mood of 52 healthy women showed that a short fast of 18 hours leads to significant mood shifts. On one hand, the women reported that the fast became harder as they grew hungrier, but they also reported an increased sense of control, pride, and achievement after successfully completing the fast.

In sports, fasting is often a way to achieve rapid weight loss and "make" a desired weight class. A study tracking young wrestlers concluded that following rigorous weight reduction regimens (more than 5% of total weight), a decline in cognitive performance and mood occurs. This can be linked to a drop in blood sugar levels, total blood volume, sleep disruption, and many other factors. Another study tracking weightlifters concluded that during a 48-hour fast, anger increased, but certain cognitive abilities simultaneously improved, while no changes were observed in memory or learning new things. Rigorous weight-loss regimens involve cutting water, so the lack of hydration could be responsible for the contradictory results of these and other studies.

I would conclude that the effects of starvation on our mood and psychological status are mostly connected to our personal perception of the fast and lack a clear biochemical mechanism. Proof of this comes from an excellent research study which proved that when people starve for two days but are unaware of it, there is no decline in cognitive performance, activity, sleep, or mood changes. With this, we prove that the factors influencing the psychological effects of fasting are essentially dependent only on our perception, namely:

• Religious Context - People who fast for religious reasons often have a more positive experience because fasting holds a deeper meaning for them, and they accept it with less stress. Conversely, those who fast for other reasons may feel greater mental pressure and discomfort.

• Emotional Control - Fasting requires a certain level of cognitive engagement and self-control, which can be challenging but also useful for strengthening a sense of discipline and inner power.

• Previous Experience - Individuals who have fasted before usually experience fewer negative effects, while those without prior experience frequently feel greater anxiety and fatigue during the first days of the fast.

• Initial Mental State - Individuals already suffering from stress, anxiety, or depression might experience a mood improvement during fasting, while those already in a stable emotional state often see no significant changes.

Fasting as a Tool in Contemporary Life

Today, food and the opportunity to enjoy it are accessible at any moment, which is why fasting is perceived as something outdated and impractical. However, our understanding of the human body and a growing body of research indicate that fasting can be a powerful tool for addressing a whole range of modern life problems. Whether it is physical and mental health, willpower training, or even slowing down aging, starvation has the potential to help and connect a person with their own needs and body.

Modern food is not only constantly available, but it is also largely enriched with extra energy through added fats and sugars. This has caused a true epidemic of chronic calorie poisoning, which has further led to a massive rise in preventable diseases, including insulin resistance, metabolic disorders, heart disease, and more. Also, problems with body dissatisfaction, overeating, depression, and other mental health challenges can be traced back to the same source. Fasting can be easily utilized to reset these habits and give our organism a break from continuous food processing, enabling better appetite management and improving our relationship with food.

Through controlled food deprivation, starvation can help develop discipline, strengthen self-control, and improve focus. As someone who frequently practices starvation, I can guarantee that when you are truly hungry, even by your own choice, all other problems become smaller and easier. I would say that fasting allows us to take a step back and more objectively consider our habits, decisions, and life as a whole. If you decide to try some form of prolonged starvation, you will observe your dependency on chewing and realize that we often bury problems that aren't hunger with food.

Another significant advantage of fasting is that it requires no preparation, is simple, and easily adapts to all responsibilities and the unpredictability of life. This makes it an exceptionally flexible tool for working on your habits and dietary improvements. Many clients I work with do not have the time to truly dedicate themselves to their diet, but with intermittent fasting, all they have to do is not eat for a while, so besides a lack of will or desire, there is no other obstacle.

Conclusion

Fasting is not just an ancient tradition or a passing trend; it is deeply rooted in human biology, evolution, and culture. Since ancient times, it has represented a way to adapt to scarcity, a means of spiritual growth, and a tool for preserving health. Today, in a world of abundance and non-stop food availability, its value has not diminished in the slightest.

As a metabolic mechanism, fasting activates processes that optimize fat burning, stabilize blood sugar levels, and improve metabolic flexibility. In addition, it shows potential benefits for longevity and the prevention of chronic diseases. However, its impact is not only physiological; it can improve mental health, assist in discipline, and increase control over one's own habits.

The psychological effects of fasting are complex and vary from person to person. While it brings a sense of achievement and inner strength to some, it can present a challenge to others. The difference lies in the context in which a person frames the fast. When practiced with purpose and understanding, it can be a powerful tool for recognizing one's own needs, emotions, and food dependencies.

In a contemporary lifestyle, fasting can serve as a simple, flexible, and effective strategy for resetting metabolism, improving the relationship with food, and strengthening mental resilience. This period of starvation does not need to be long-term or extreme, as even an intermittent fast lasting less than 24 hours brings significant benefits.

In the end, fasting is not a magical solution nor a universal practice that suits everyone. It is a tool, and like any tool, its value depends on how it is used. For this reason, I do not recommend starvation to most of my clients—sometimes because I think it will be too difficult for them, and sometimes because I worry they will overdo it and somehow misuse fasting as an easy way to feel better about a poor diet. However, when applied purposefully and tailored to individual needs, fasting can contribute to health, focus, and better control over one's own body and mind.

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