Fasting has become one of the most talked–about trends in the health world in recent years. There are those who swear by intermittent fasting to lose weight, others do so for religious or spiritual reasons, and there are also quite a few studies trying to understand whether abstaining from food can truly improve health.
However, a new study now manages to shed unprecedented light on what occurs in the body during a prolonged fast, and the results managed to surprise even the researchers themselves.
The study, published in the scientific journal Nature Metabolism, tracked 12 healthy volunteers who performed a full water fast for seven days. During this period, researchers collected blood samples from them daily and tested approximately 3,000 different proteins in the body to understand how the body responds at the molecular level.
The findings showed that the body does indeed begin shifting to burning fat as early as the first two days of the fast, but the most interesting and profound changes actually appeared only after about three days without food.
According to the researchers, it appears that at this stage, the body enters a completely new biological state, which goes beyond regular fat burning.
The body switches "operating mode"
When a person eats normally, the body primarily uses glucose coming from food as a central energy source. But during a prolonged fast, sugar stores are depleted and the body is forced to switch to using fat stored in tissues.
This transition is not new to scientists. Humans evolved over thousands of years to survive periods of food shortage, and therefore the body has biological mechanisms that enable it to cope with hunger.
However, the new study reveals that the process is much deeper than previously thought. During the fast, significant changes were observed in the activity of more than a third of the tested proteins in the body. Some of the changes were related to the immune system, metabolism, and even to structures that support nerve cells in the brain.
The researchers were particularly surprised that the changes appeared almost identically in all participants, something that suggests that the body activates an orderly and well–organized biological program during a prolonged fast.
Rapid weight loss, but not only
The participants in the study lost an average of about 5.7 kilograms during the seven days of the fast. Part of the loss was from fat, but another part also stemmed from the loss of muscle mass and fluids.
However, after three days in which they returned to eating normally, most of the muscle mass returned, while a significant portion of the burned fat remained lower.
But the researchers emphasize that weight loss is only a small part of the story. According to them, the discovered biological changes may be related to broader processes such as reducing inflammation, improvement in metabolic function, and even certain protection for the brain.
<br>What happens to the brain during fasting?
One of the most intriguing findings was the change in proteins related to the nervous system and structures that support brain cells. According to the researchers: It is possible that prolonged fasting affects repair and renewal mechanisms in the brain, although it is still not entirely clear what the clinical significance of the findings is.
In recent years, scientific interest has been growing in the possible connection between fasting and brain health. Previous studies have already raised the possibility that intermittent fasting may improve insulin sensitivity, reduce inflammation, and improve certain cellular processes.
The current study strengthens the hypothesis that fasting affects many systems in the body simultaneously, and not just weight.
Despite the intriguing findings, researchers warn that prolonged fasting is not suitable for everyone. A fast of several days without food can be dangerous for people with chronic diseases, diabetes, eating disorders, pregnant women, and people taking certain medications.
Even in healthy people, a long fast can cause weakness, dizziness, a drop in blood pressure, headaches, and sometimes also heart rhythm disturbances. Therefore, experts emphasize that a prolonged fast should not be performed without appropriate medical supervision.