Background: Fasting, the voluntary abstention from all restricted foods has long become the feature of many religions. However; little is known about the health and aging benefits, if not for some traditional legends. Promisingly, in the past couple decades; a rise in the number of investigations examining the health-related effects of religiously motivated fasting has been reported. In the present study, we aimed to review available evidences about the metabolic and aging effects of religiously proclaimed fasting, emphasizing experiences of Orthodox Churches worldwide.

Findings: According to many of the reviewed studies, Orthodox Christians fast between 180 - 200 days each year, varying across countries. It was reported that there is a strong associations between fasting ascribed for religious purposes with several metabolic and health outcomes. The metabolic effects of fasting were observed in the form of lowered total cholesterol and LDL-C levels, and LDL-C/HDL-C ratios; reduced respiratory-exchange ratio, greater metabolic flexibility, and efficiency of energy production from fatty acids and ketone bodies. Fasting diabetic patients had significantly lowered levels of glucose, triglycerides (TG) and TG/ high-density lipoprotein ratio, while declining blood urea nitrogen (BUN), and BUN/creatinine ratio as well as low uric acid. Due to enhanced activation of intrinsic defenses against oxidative and metabolic stress and removal; as well as repair of damaged molecules, fasting was associated with boosted immunity and longer age.

Conclusions and Recommendations: Adherence to fasting ascribed by religions, particularly the Orthodox Church was seen to be yield beneficial metabolic outputs, healthy and longer life.  Further studies are needed to uncover additional health benefits and any potential adverse effects across population and age groups. With the available evidence, it’s possible to recommend that health systems in the 21^st century consider fasting as key part of health promotion activities, particularly to mitigate the alarmingly rising obesity, chronic and non-communicable diseases.