Fasting diets show promise in enhancing mood, sleep, and eating behaviors

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In a recently published review Dr Frontiers in nutrition, researchers summarized current scientific knowledge on how fasting diets (FDs) affect eating behavior, mood, sleep, and overall well-being. Their findings highlight potential mechanisms underlying the beneficial effects of FD, an important mechanism being the gut microbiome.

Dishes and cutlery plates decorated with a clockwork imitation
Study: Fasting Diets: What Effects on Eating Behavior, Sleep, Mood, and Well-Being? Image credit: Marcin Malicki/

To identify relevant papers, the researchers conducted a systematic literature search across scientific databases such as Web of Science and PubMed using keywords related to FD regimens and outcomes related to physical and mental well-being.

Fasting is known to have several health benefits

FDs have been used since the early 5m When Greek physician Hippocrates suggested avoiding food or drink to treat convulsions in the 10th century BC. Compared to dietary regimens that require calorie restriction (CR), FDs are considered easier to follow and more satisfying.

There are several rules by which FD is implemented, but all require at least eight hours of fasting daily. A popular diet, 5:2 Intermittent Fasting (IF), involves two non-consecutive fasts per week and not restricting meal times for the other five.

Followers of intermittent fasting follow their regular diet 5-6 days a week and limit their food intake the rest of the time. Alternate day feeding (ADF) restricts food intake to a specific window every other day. There are also religious and cultural reasons for following FD, such as during the Muslim holy month of Ramadan.

FDs have attracted scientific attention as a potential strategy to lower serum glucose, reduce hepatic oxygenation, and induce glycolysis to alter ketogenesis in the body. Research suggests that FDs can help with weight control and protect against type 2 diabetes, cancer, cardiovascular disease, multiple sclerosis (MS), Alzheimer’s disease (AD), Parkinson’s disease (PD), stroke, and epilepsy.

They may also promote mental health by reducing anxiety and improving cognition. However, these effects and eating behaviors have not been the subject of as much research focus.

Studies have found opposite effects of FDs on eating behavior

Weight management strategies can moderate eating behaviors associated with obesity. On the CR diet, subjects may compensate by overeating and regain lost weight. Some studies show that following a FD leads to increased hunger, compensatory eating, and weight regain compared to CR, while others find that the two strategies are equivalent.

In some studies, the effects were seen only in the short term but not in the long term, indicating the difficulty of continuing to follow any diet. Individuals who fast during Ramadan have significantly different experiences of eating behavior, reporting lower levels of hunger at the end of the month.

Similarly, studies examining the effects of FD on disinhibition and dietary restraint have yielded mixed results. Some papers have shown that CR is associated with flexible restraint, which is a more graduated approach, leading to less obesity and binge eating, while FDs often follow a more rigid ‘all or nothing’ approach, which may lead to overeating. Others found no difference in emotional eating between the ADF regimen and the regular diet.

The reviewers suggest that these included findings may be due to a lack of uniformity across studies, including differences in sample size, study population, intervention duration, and study design. Younger individuals appear to be more likely to overeat during FD than middle-aged individuals.

Several studies did not have a control group, and none explored the effect of FD on satiety. Further systematic studies using comparative study designs and analyzes are needed to evaluate the effectiveness of FDs in improving eating behavior over short and long periods.

FDs modulate sleep-wake patterns and significantly improve mood

Although FDs cause circadian rhythm disturbances, some studies have not significantly affected insomnia severity or sleep duration, while others have found them to improve sleep quality.

A study found that people who fast during Ramadan sleep more during the day. There are some indications that FDs may be a promising way to reduce disruptions to circadian rhythms due to sleep-disrupting health conditions or work shifts, but this requires further investigation.

In terms of effects on mood, FDs significantly reduce anger, confusion, agitation, depression, and overall mood disturbances while increasing energy levels. A similar effect was observed among those fasting during Ramadan. However, these results were seen in the short term; Future studies may examine the effect of FD on improving mood in the long term.

Gut-brain interactions may underlie the effects of FD

The gut-brain axis may be instrumental in driving the effects of FD, particularly on mood. Gastrointestinal complaints are common in people with depression and anxiety, pointing to a complex connection between brain health and gut function.

Intermittent fasting has been shown to improve gut health, which is then associated with active metabolism and higher production of neurotransmitters. Another mechanism by which FD improves mood may be through increased production of ketone bodies.

The literature suggests that FDs may be most effective with adequate sleep and by synchronizing meal times with the body’s circadian rhythm.

However, more studies are urgently needed to provide science-driven recommendations for incorporating FDs into regimens to combat obesity and improve the quality of life of individuals living with cardiovascular disease and other health conditions.

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