Today, nutrition is often reduced to calorie counting, macronutrient distributions, and popular diet trends. However, fasting, a practice thousands of years old, makes us reconsider a more fundamental question: What truly nourishes us?
Fasting shows remarkable continuity across different geographies and religious traditions. Ramadan in Islam, Lent in Christianity, Yom Kippur in Judaism… Is the emergence of a similar practice in so many different cultures a coincidence, or does it point to a deeper truth about human nature? The answer to this question lies at the intersection of biology and the world of meaning.
Biologically, the human body is far more dynamic than we think. Within weeks, 70-90% of the atoms that make up our bodies are renewed. In this sense, humans are more like a constantly flowing river than a static structure. What we call “us” today was not long ago a part of plants, animals, or the air. What we eat transforms us. But perhaps an equally important truth is that what we don’t eat also shapes us. The 19th-century philosopher Ludwig Feuerbach said, “Man is what he eats.” Perhaps today it’s time to expand on this statement: Man is shaped not only by what he eats, but also by what he consciously chooses not to eat.
The words of the Prophet Muhammad are noteworthy in this context: “The son of Adam has never filled a vessel worse than his stomach.” This statement is not only about nutrition; it contains a powerful message about moderation, self-control, and consumption ethics. In this sense, fasting is not just about going hungry. Fasting is the practice of creating distance between desires and actions. Postponing immediate desires allows the individual to reposition themselves both physically and mentally. This process can provide not only metabolic flexibility but also psychological and moral discipline.
Fasting leads to well-organized metabolic changes in the body. After approximately 12–16 hours of fasting, the organism switches from glucose utilization to fat burning. Glycogen stores in the liver are depleted, insulin levels decrease, and fatty acids are mobilized. During this process, ketone bodies are produced in the liver. Thus, fat is burned, providing an alternative energy source for the brain.
Beyond its effects on energy metabolism, fasting is thought to have cellular effects. The most debated of these is autophagy. Autophagy is an “internal cleaning” mechanism in which the cell breaks down and recycles damaged structures. This mechanism has been strongly demonstrated, particularly in animal experiments (https://livehelfi.com/blogs/all/discover-the-benefits-of-autophagy).
Clinical studies suggest that intermittent fasting, particularly Ramadan-type fasting, may improve some metabolic markers. A systematic review by Faris et al. shows that fasting may be associated with increased insulin sensitivity, decreased inflammatory markers, and an average decrease of 3–5 mmHg in systolic blood pressure (https://pubmed.ncbi.nlm.nih.gov/31581955/). Similarly, a meta-analysis by Sadeghirad et al. reports an average weight loss of 1–2 kilograms during Ramadan (although this effect is often temporary) (https://pubmed.ncbi.nlm.nih.gov/23182306/).
However, these findings have a significant limitation: Fasting does not automatically lead to a healthy outcome. Dietary habits during non-fasting hours are crucial. Factors such as excessive calorie intake, high sugar consumption, and irregular sleep can negate or even reverse the potential benefits of fasting. Furthermore, fasting is not suitable for everyone. For diabetics, individuals with eating disorders, pregnant women, and those with certain chronic illnesses, fasting can pose serious health risks. Therefore, any assessment of fasting should include its limitations and risks as well as its benefits.
However, evaluating fasting solely on its physiological effects would overlook the true depth of this practice. Ultimately, believers fast not for the benefits it provides, but because of their faith. From a religious perspective, fasting is not only an act of worship but also part of a way of life. Humans are incredibly complex beings. Even the simplest machines have instruction manuals, so how reasonable is it to leave humans completely without guidance? From this point of view, we can say that prophets were not only spiritual guides but also bearers of a system for the practical aspects of life.
Fasting can become even more meaningful, especially for displaced individuals, those adapting to different countries, or those facing academic pressures. It can provide a sense of continuity, order, and control amidst feelings of fragmentation. When practiced correctly and consciously, it is neither merely a religious ritual nor simply a biological intervention. It bridges the gap between these two realms. Fasting invites us to consider the individual as both a biological organism and a being searching for meaning.