Gaby
Millions of people around the world lose weight through diets or religious fasting. But the biological consequences of prolonged calorie restriction have been poorly understood.
A team of scientists from Germany, the UK, Norway, and Denmark looked at the systemic changes that occur in different organs during extended periods without food. They found both benefits and risks, as reported by IFLScience.
What the Researchers Learned
The authors of the study recruited 12 healthy volunteers for a seven-day fast. Participants were allowed to drink water but could not eat. Throughout the experiment, the researchers closely monitored the volunteers’ health. They measured daily changes in roughly 3,000 blood proteins. These proteins are the fundamental building blocks for cells and tissues in the body.
The authors noted that within the first few days of fasting, the volunteers’ bodies shifted their energy source: they began burning stored fat instead of glucose. As a result, participants lost an average of 5.7 kilograms over the week. That weight loss persisted even after the volunteers resumed eating.
However, to their surprise, the researchers did not observe significant changes in blood protein levels during the initial days of fasting. The situation changed after the third day, when levels of hundreds of proteins that affect health began to fluctuate.
The scientists compared their findings with genetic studies that linked various blood plasma proteins to different diseases. This allowed them to assess the health implications of the changes in 212 proteins observed during fasting.
For example, they found that abstaining from food for more than three days led to a decrease in the protein SWAP70. Lower levels of SWAP70 are associated with a reduced risk of developing rheumatoid arthritis (RA), and the researchers suggested this could at least partially reduce pain for RA patients.
They also observed a decrease in the protein HYOU1, which is linked to ischemic heart disease. The team says intermittent fasting may therefore have beneficial effects on heart health.
At the same time, the researchers identified several negative consequences. For example, they observed increased blood clotting, which raises the risk of thrombosis.
“For the first time, we saw what happens at the molecular level in the body when we fast,” said study author Claudia Langenberg. “Our results showed health benefits of fasting beyond weight loss, but these benefits were only noticeable after three days of complete calorie restriction—later than we expected,” she added.
Summarizing the findings, Mike Pitzner, another author of the study, noted that “while fasting can be beneficial for treating certain conditions, it often isn’t suitable for patients with health issues.”
The results of the study were published in the journal Nature Metabolism.
