Fasting has a long list of health benefits. While weight loss is a popular reason for fasting, it is likely the least important result of fasting.
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Fasting appears to have a long list of potential health benefits. While weight loss is a popular reason for fasting, the truth is this is likely the least important (and least effective) result of fasting. So let’s go through a list of some of the health benefits of fasting researchers and clinicians have uncovered to date and see what fasting could do for our health and bodies.
A study performed earlier this year showed that fasting decreases the enrichment of gut microflora responsible for colitis symptoms and suppresses inflammation in mice colon and brain (1). Together, their results showed extensive effects of fasting on both digestive and psychological disorders that currently have few treatment options.
Unhealthy eating, like a high-fat diet, disrupt our circadian rhythm. Mice fed a high-fat diet had a dysfunctional circadian rhythm, meaning their day/night cycle was confused. Our body runs all organs, cognition, hormones, and systems on this day/night clock. Metabolic diseases, hormonal disorders, and other problems occur when the circadian rhythm is disrupted. While fasting mice did not eat less overall, they did have fewer metabolic problems and physiological changes consistent with healthier diets than the high-fat diet they had been fed (2). This suggests fasting may help to reset and normalize a dysfunctional circadian rhythm, which would be a great thing for overall health.
Fasting could help reset your circadian rhythm, helping you sleep better at night.
Gut microbiota change during fasting, which has a significant impact on health. The gut microbiome has interested those in the obesity field for decades because obese individuals have extremely different compositions of microbes in their digestive tract (3). This changes the way their body extracts calories and utilizes the foods they eat. If fasting changes the gut microbiome, decreasing inflammatory bacteria in the gut, and perhaps reversing diseases that this weight-related dysregulation causes, it could be another way to combat obesity-related disease (4).
Some studies in mice have shown that pairing intermittent fasting with radiation and chemotherapy increased its effect and made the intervention more effective at reducing and eliminating cancer. Intermittent fasting is also thought to reduce the toxicity of these cancer treatments, which could also boost survival. In humans, intermittent fasting might reduce gastro-intestinal side-effects and fatigue. Also, fasting regiment doesn’t seem to have any detrimental effect on chemotherapy treatment (5). Further research is needed in this field.
Fasting can reduce the intake of cholesterol and fat, which has a secondary benefit. For those with cardiovascular disorders, this may be a way to improve vascular health, reduce cholesterol, and improve heart health (6). In a recent study in mice, those with a high-fat diet and poor cardiovascular health improved their heart and vascular health when they underwent intense fasting. The researchers suggest this could be because intermittent hunger increased caspase 3, which is involved in apoptosis and autophagy of heart tissue, which is our body’s way of eliminating dying or damaged cells, keeping the whole organ system healthy and functioning well (7).
Some studies in mice and humans have shown that fasting has some effects on the brain network that helps us think and retain memories. This makes sense because our brain lives off of glucose from our diet to function and run its cells. When fasting, glucose metabolism is occurring at a very low rate, changing the way these cells communicate and function. A study done in human trials showed that the thalamus and basal ganglia in the brain (these are most responsible for working memory, which is our short term memory space) exhibit less activity and multiple changes during a fasting state. Low glucose levels, the researchers conclude, might reduce memory and cognition ability, as these areas of the brain require high levels of glucose to run (8). However, other groups have found that fasting may improve the brain’s ability to regenerate neurons, which improves cognition and brain signaling (9). The question of the effect of fasting on cognition remains a mystery for now!
One of the top reasons why people fast beyond wanting to lose weight is because they’ve heard the rumors that cutting enough calories can increase your lifespan. Male mice who fasted did live longer than mice allowed to eat more frequently in a 2018 study (10). In fact, caloric restriction is touted as one of the best ways to live longer because of toxic by-products of our metabolism, such as free-oxygen radicals (which can go on to develop into cellular and organ problems and even cancer) (11). However, human studies are rare, and those that have been performed remain controversial. Moreover, fasting and caloric restriction are two different eating regimens. Caloric restriction is defined as a 30% reduction of caloric intake every day, while fasting is the complete absence of food for a variable amount of time. It’s difficult to say whether caloric restriction is the key to longer lifespans, primarily because there are many reasons why we age the way we do (12, 13). Our lifespan is determined by our genes, environment, immune system, and many other factors. It is nearly impossible to say that one specific thing could make our lifespan longer. But, lowering cholesterol, reducing weight, boosting immune responses, improving neuron and brain health, and improving gut and heart health means you are a healthier you, and that’s certainly a worthwhile cause!
More questions? Check out “Satia’s Complete Guide to Fasting.”
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