New findings reveal that the body undergoes significant systematic changes in multiple organs during prolonged periods of fasting. The results demonstrate evidence of health benefits beyond weight loss, but also show that any potentially health-altering changes appear to occur only after three days without eating.
The study, published today in nature metabolism, improves our understanding of what happens throughout the body after prolonged periods without eating.
By identifying the potential health benefits of fasting and their underlying molecular basis, researchers from the Precision Healthcare University Research Institute (PHURI) at Queen Mary University of London and the Norwegian School of Sports Sciences provide a roadmap for future research. that could lead to therapeutic interventions. – even for people who can benefit from fasting but cannot undergo prolonged fasting or diets that mimic fasting, such as ketogenic diets.
Over millennia, humans have developed the ability to survive without food for extended periods of time. Fasting is practiced by millions of people around the world for different medical and cultural purposes, including health benefits and weight loss. Since ancient times it has been used to treat diseases such as epilepsy and rheumatoid arthritis.
During fasting, the body changes its source and type of energy, going from consumed calories to using its own fat reserves. However, beyond this change in fuel sources, little is known about how the body responds to prolonged periods without food and the health impacts, beneficial or adverse, this may have. New techniques that allow researchers to measure thousands of proteins circulating in our blood provide the opportunity to systematically and in great detail study the molecular adaptations to fasting in humans.
The researchers followed 12 healthy volunteers who participated in a seven-day water-only fast. The volunteers were closely monitored daily to record changes in the levels of around 3,000 proteins in the blood before, during and after fasting. By identifying which proteins are involved in the body’s response, researchers could predict the potential health outcomes of prolonged fasting by integrating genetic information from large-scale studies.
As expected, the researchers observed that the body switched energy sources (from glucose to fat stored in the body) within the first two to three days of fasting. The volunteers lost an average of 5.7 kg of both fat and lean mass. After three days of eating after fasting, the weight was maintained: the loss of lean mass was almost completely reversed, but the fat mass was maintained.
For the first time, researchers observed that the body experienced distinct changes in protein levels after approximately three days of fasting, indicating a whole-body response to complete caloric restriction. Overall, one in three of the proteins measured changed significantly during fasting in all major organs. These changes were consistent among volunteers, but there were distinctive signatures of fasting that went beyond weight loss, such as changes in proteins that form the supporting structure of neurons in the brain.
Claudia Langenberg, director of Queen Mary’s Precision Health University Research Institute (PHURI), said:
“For the first time, we can see what happens at a molecular level throughout the body when we fast. Fasting, when done safely, is an effective weight loss intervention. Popular diets that incorporate fasting, such as intermittent fasting , – claim to have health benefits beyond weight loss. Our results provide evidence of the health benefits of fasting beyond weight loss, but these were only visible after three days of total calorie restriction, later than we previously thought.
Maik Pietzner, chair of health data at PHURI and co-director of the computational medicine group at the Berlin Health Institute at Charité, said:
“Our findings have provided a basis for some ancient knowledge about why fasting is used for certain conditions. While fasting can be beneficial in treating some conditions, many times, fasting will not be an option for patients suffering from “We hope that these findings can provide information about why fasting is beneficial in certain cases, which can then be used to develop treatments that patients can take.”