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LONDON — The body experiences significant, and systematic changes across multiple organs during prolonged periods of fasting, a new study revealed on Friday.
The study, published in the journal Nature Metabolism, demonstrated evidence of health benefits beyond weight loss but also showed that any potentially health-altering changes appear to occur only after three days without food.
Researchers from the Queen Mary University of London and the Norwegian School of Sports Sciences have identified potential health benefits from fasting, which could lead to therapeutic interventions for people who cannot undergo prolonged fasting or fasting-mimicking diets.
"Our findings have provided a basis for some age-old knowledge as to why fasting is used for certain conditions. While fasting may be beneficial for treating some conditions, often times, fasting won’t be an option for patients suffering from ill health," said Maik Pietzner, professor at Queen Mary University.
Researchers followed 12 healthy volunteers taking part in a seven-day water-only fast.
The volunteers were monitored closely on a daily basis to record changes in the levels of around 3,000 proteins in their blood before, during, and after the fast.
The researchers observed the body switching energy sources -- from glucose to fat stored in the body -- within the first two or three days of fasting. The volunteers lost an average of 5.7 kg of both fat mass and lean mass.
After three days of eating after fasting, the weight stayed off -- the loss of lean was almost completely reversed, but the fat mass stayed off, the study noted.
"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," said Claudia Langenberg, Director of Queen Mary’s Precision Health University Research Institute (PHURI).
The researchers noted that the results provided evidence for the health benefits of fasting beyond weight loss, but these were only visible after three days of total caloric restriction - later than they previously thought.