Fasting for 7 days... Scientists reveal unexpected effects

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The effect of abstaining from food for several days is not limited to forcing the body to burn stored fat, but also extends to causing broad biological changes that include multiple organs and systems, while a study revealed that many of these changes do not appear clearly until about three days have passed without eating calories.

The results provide a detailed picture of how the human body responds to prolonged fasting, while revealing effects that go beyond weight loss and changes related to the metabolism. They also open the way for future research that may help develop treatments that mimic some of the biological effects of fasting, without the need to abstain from food for long periods, according to a report published by the “ScienceDaily” website, about the study published in the “Nature Metabolism” journal.

In addition, the study was conducted by scientists from the Precision Healthcare Research Institute (PHURI) at Queen Mary University of London and the Norwegian School of Sports Sciences. By identifying the molecular changes associated with fasting, the researchers seek to lay the foundation for future studies that may contribute to the development of treatments that mimic some of its effects, which may benefit people who could benefit from these effects, but who cannot safely undergo extended fasting.

They believed that humans had evolved to be able to endure long periods without food, an ability that was necessary in times when obtaining meals was not guaranteed. Today, millions of people fast for religious, cultural, or medical reasons, or for the purpose of losing weight. Fasting also has a long history in the medical field, having been used in various forms to help manage multiple health conditions, including epilepsy and rheumatoid arthritis.

One of the most prominent changes that occur during fasting is the shift in the energy sources that the body relies on. Under normal circumstances, the body obtains most of its energy from glucose derived from food, and as abstinence from eating continues and available energy sources are exhausted, it gradually begins to rely more on stored fat.

Although scientists knew about this basic metabolic shift, the effect of prolonged fasting on the rest of the body remained less clear, especially with regard to biological changes that may be beneficial or harmful, or a combination of both.

Modern techniques for analyzing proteins have also made it possible to study these effects in more detail and accuracy, as proteins perform various functions in the body, including building tissues, regulating chemical reactions, and transmitting signals between cells. Hence, measuring thousands of proteins in the blood provides a broad picture of how different organs and biological systems respond to fasting.

The results of the study showed that the effect of prolonged fasting extends to a broader range of biological processes, and is not limited to changes associated with fat metabolism. Claudia Langenberg, director of the Precision Healthcare Research Institute at Queen Mary University of London, said that the study allowed for the first time to see what happens at the molecular level throughout the body during fasting.

She also added that fasting, when practiced safely, can be an effective way to lose weight, while common diets that include fasting, such as intermittent fasting, indicate health benefits beyond weight loss. She explained that the results of the study provide evidence of potential health effects that go beyond weight loss, but they did not appear clearly until after three days of complete abstinence from eating calories, which is a longer period than previously thought.

Note that the timing of these changes is of particular importance when interpreting the results, as intermittent fasting usually involves shorter periods of abstinence from food, while the study looked at complete calorie restriction over several days. Therefore, the results do not mean that shorter periods of fasting will necessarily produce the same biological effects.

Instead, the study helps determine the point at which some of the most important molecular responses associated with prolonged fasting begin to emerge, allowing a more precise understanding of the differences between its effects on metabolism and the broader changes that occur in the body.

Understanding the mechanisms responsible for the biological changes induced by fasting may ultimately be more important than fasting itself, as identifying molecular pathways associated with potential beneficial effects may pave the way for developing treatments that activate these pathways without the need to abstain from food for several days.

This approach may represent an important option for people whose health conditions prevent the practice of long-term fasting safely, or make it impractical to adhere to it.

That's why Mike Pitzner, head of health data at PHURI and co-leader of the computational medicine group at the Berlin Health Institute of the Charité Hospital, said that the results provide a scientific basis for some of the previous knowledge about why fasting is used to treat certain health conditions.

He added that fasting, although it can be useful in dealing with some cases, is not an option for many patients who suffer from health problems. He expressed his hope that the results will help explain the reasons for the benefit of fasting in specific cases, allowing this knowledge to be used in developing treatments that patients can use in the future.

The study provides a detailed molecular map of how the human body adapts to prolonged fasting, and highlights an important difference between early metabolic shifts and broader biological changes. While the body begins to rely more on stored fat during the first days of fasting, many of the other associated changes do not become clearly detectable until about three days have passed without consuming calories.

This distinction helps researchers separate changes associated with weight loss from the broader biological responses elicited by prolonged fasting, and provides a basis for studying the possibility of mimicking these responses in the future, without the need to subject people to long periods of abstinence from food.