Recent research indicates that extended durations of fasting cause the body to go through major, systematic changes in a number of organs. The findings indicate that there are health benefits that go beyond weight reduction, but they also suggest that any potentially transformative effects on health seem to happen only after three days without meals.
Though the results also indicate that any potentially health-altering changes seem to occur only after three days without meals, they do provide evidence of health advantages beyond weight loss.
Our understanding of the body’s reactions to extended fasts without food is improved by this study, which was published in Nature Metabolism.
Researchers from the Norwegian School of Sports Sciences and Queen Mary University of London’s Precision Healthcare University Research Institute (PHURI) have identified the potential molecular basis for health benefits associated with fasting and have provided a roadmap for future research that may lead to therapeutic interventions. This includes people who may benefit from fasting but are unable to follow prolonged fasting or diets that mimic fasting, such as ketogenic diets.
Humans have evolved over millennia to be able to go extended periods of time without nourishment. Millions of individuals worldwide fast for a variety of cultural and medical reasons, including weight loss and general health advantages. It has been used to treat illnesses like rheumatoid arthritis and epilepsy since ancient times.
The body uses its own fat stores instead of absorbed calories as its primary energy source while fasting. Beyond this shift in fuel sources, however, little is understood about how the body reacts to extended fasts without food and the potential positive or negative effects this may have on health. The ability to test thousands of proteins in our blood thanks to new technology has made it possible to thoroughly and methodically explore how human biochemical adaptations to fasting work.
Twelve healthy participants in a seven-day water-only fast were observed by researchers. Before, during, and after the fast, the volunteers’ blood levels of almost 3,000 different proteins were regularly measured and recorded. The researchers may then integrate genetic data from many studies to forecast the health consequences of extended fasting by identifying which proteins are involved in the body’s reaction.
The body naturally switched from using glucose as energy to using body fat during the first two or three days of fasting, as the researchers had predicted. Both lean and fat mass were reduced by the individuals on average by 5.7 kg. The weight loss was nearly entirely reversed after three days of eating after fasting, but the reduction in fat mass persisted.
After roughly three days of fasting, the researchers saw the body experiencing noticeable alterations in protein levels for the first time, demonstrating a whole-body reaction to stringent calorie restriction. Across all major organs, one in three of the studied proteins had significant changes during fasting. These alterations were similar for all of the volunteers, although fasting had additional hallmarks besides weight loss, such as modifications to the proteins that support brain neurons.
Director of Queen Mary’s Precision Health University Research Institute (PHURI), Claudia Langenberg, stated: “For the first time, we’re able to see what’s happening on a molecular level across 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 for the health benefits of fasting beyond weight loss, but these were only visible after three days of total caloric restriction—later than we previously thought.”
The co-leader of the Berlin Institute of Health at Charité’s Computational Medicine Group and PHURI’s Health Data Chair, Maik Pietzner stated, “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, oftentimes, fasting won’t be an option to patients suffering from ill health. 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 are able to do.”