In a recent review published in Frontiers in Nutrition, researchers summarized the present scientific knowledge on how fasting diets (FDs) affect eating behaviors, mood, sleep, and overall well-being. Their findings highlight the potential mechanisms underlying the useful effects of FDs, one crucial mechanism being the gut microbiome.
To discover relevant papers, researchers conducted a scientific literature search across scientific databases equivalent to Web of Science and PubMed using keywords related to FD regimens and outcomes related to physical and mental well-being.
Fasting is understood to have several health advantages
FDs have been used since as early because the 5th century BCE when the Greek physician Hippocrates prescribed abstaining from food or drink to treat seizures. In comparison with dietary regimens that require calorie restriction (CR), FDs are perceived as being easier and more satisfying to follow.
There are several regimens through which FDs are implemented, but all require a minimum of eight hours of fasting day by day. A well-liked eating regimen, 5:2 intermittent fasting (IF), involves two non-consecutive days of fasting per week while not restricting food timings through the other five.
Followers of periodic fasting follow their regular diets for 5-6 days every week while limiting their food intake through the remainder. Alternate day feeding (ADF) restricts food intake to a particular window every other day. There are also religious and cultural reasons for following FDs, e.g., through the Muslim holy month of Ramadan.
FDs have drawn scientific attention as a possible strategy to cut back serum glucose, deplete hepatic oxygen, and produce about glycolysis to ketogenesis shift within the body. Research suggests that FDs could help control weight and be protective against type 2 diabetes, cancer, heart problems, multiple sclerosis (MS), Alzheimer’s disease (AD), Parkinson’s disease (PD), stroke, and epilepsy.
They may promote mental health by reducing anxiety and improving cognition. Nonetheless, these effects and people on eating behaviors haven’t been the topic of as much research focus.
Studies found contradictory effects of FDs on eating behaviors
Weight management strategies can moderate eating behaviors which can be related to obesity. In CR diets, subjects may compensate by overeating and regaining lost weight. Some studies suggest that following an FD can result in lower feelings of hunger, compensatory eating, and weight regain than CRs, while others find that the 2 strategies are equivalent.
In some studies, the consequences were seen only within the short term but not over longer periods, pointing to the issue of constant to follow any dietary regimen. Individuals fasting during Ramadan have markedly different experiences by way of eating behavior, reporting lower levels of hunger at the tip of the month.
Similarly, various results were obtained in studies examining the effect of FDs on disinhibition and dietary restraint. Some papers found that CR is related to flexible restraint, which is a more graduated approach, resulting in lower adiposity and binge eating, while FDs often follow a more rigid ‘all or nothing’ approach, which may cause overeating. Others have found no difference in emotional eating between ADF regimens and regular diets.
The reviewers suggest that these inclusive findings might be as a result of the shortage of uniformity across different studies, including differences in sample size, study populations, intervention duration, and study design. Younger subjects appear more more likely to overeat during FDs in comparison with middle-aged individuals.
Several studies didn’t have control groups, and none explored the effect of FDs on satiation. Further systematic study using comparable study designs and analyses is required to evaluate the efficacy of FDs in improving eating behaviors over short and long periods.
FDs modify sleep-wake patterns and significantly improve mood
While FDs cause misalignments in circadian rhythms, some studies haven’t found them to significantly affect insomnia severity or sleep duration, while others have found them to enhance sleep quality.
One study found that individuals fasting during Ramadan exhibited more daytime sleepiness. There are some indications that FDs might be a promising solution to alleviate disturbances to circadian rhythms as a result of sleep-interrupting health conditions or shift work, but this requires further exploration.
By way of effects on mood, FDs were found to significantly reduce anger, confusion, tension, depression, and overall mood disturbance while increasing energy levels. Similar effects were seen in fasting populations during Ramadan. Nonetheless, these findings were all seen within the short term; future studies can examine the impact of FDs in improving moods in the long run.
Gut-brain interactions could underlie the consequences of FDs
The gut-brain axis could also be instrumental in driving the consequences of FDs, particularly on mood. Gastrointestinal complaints are common amongst individuals with depression and anxiety, pointing to the complex connections between brain health and gut functioning.
Intermittent fasting has been shown to enhance gut health, which is then related to higher production of energetic metabolites and neurotransmitters. One other mechanism by which FDs improve mood might be through the increased production of ketone bodies.
The literature suggests that FDs might be best in reference to adequate sleep and by synchronizing mealtimes with the body’s circadian rhythms.
Nonetheless, further studies are urgently required to supply science-driven recommendations for incorporating FDs into regimens to deal with obesity and to enhance the standard of life for people living with cardiovascular diseases and other health conditions.