The past two decades have seen a rise in the number of investigations examining the health-related effects of religiously motivated fasts. Islamic Ramadan is a 28 - 30 day fast in which food and drink are prohibited during the daylight hours. The majority of health-specific findings related to Ramadan fasting are mixed. The likely causes for these heterogeneous findings are the differences between studies in the following: 1) the amount of daily fasting time; 2) the percentage of subjects who smoke, take oral medications, and/or receive intravenous fluids; and 3) the subjects' typical food choices and eating habits. Greek Orthodox Christians fast for a total of 180 - 200 days each year, and their main fasting periods are the Nativity Fast (40 days prior to Christmas), Lent (48 days prior to Easter), and the Assumption (15 days in August). The fasting periods are more similar than dissimilar, and they can each be described as a variant of vegetarianism. Some of the more favorable effects of these fasts include the lowering of body mass, total cholesterol, LDL-C, and the LDL-C/HDL-C ratio. The Biblical-based Daniel Fast prohibits the consumption of animal products, refined carbohydrates, food additives, preservatives, sweeteners, flavorings, caffeine, and alcohol. It is most commonly partaken for 21 days, although fasts of 10 and 40 days have been observed. Our initial investigation of the Daniel Fast noted favorable effects on several health-related outcomes, including: blood pressure, blood lipids, insulin sensitivity, and biomarkers of oxidative stress. This review summarizes the health-specific effects of these fasts and provides suggestions for future research.

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The impact of religious fasting on human health

During the 9th month (Ramadan) of the Islamic calendar (Hijra) many millions of adult Muslims all over the world fast during the daylight hours. Since Hijra is a lunar calendar, Ramadan occurs at different times in the seasonal year over a 33-year cycle. Fasting during Ramadan is partial because the abstention from food, fluid, tobacco and caffeine is from sunrise to sunset. Several categories of people are exempt or can postpone the Ramadan fast. The effect on health and well being of the month-long intermittent fast and fluid restriction has been studied in various potentially vulnerable groups in addition to normal healthy individuals in many countries. The majority of the studies have found significant metabolic changes, but few health problems arising from the fast. A reduction in drug compliance was an inherent negative aspect of the fast. Common findings of the studies reviewed were increased irritability and incidences of headaches with sleep deprivation and lassitude prevalent. A small body mass loss is a frequent, but not universal, outcome of Ramadan. During the daylight hours of Ramadan fasting, practising Muslims are undoubtedly dehydrating, but it is not clear whether they are chronically hypohydrated during the month of Ramadan. No detrimental effects on health have as yet been directly attributed to negative water balance at the levels that may be produced during Ramadan.

Effects on health of fluid restriction during fasting in Ramadan

Considerable interest has been shown in the ability of caloric restriction (CR) to improve multiple parameters of health and to extend lifespan. CR is the reduction of caloric intake - typically by 20 - 40% of ad libitum consumption - while maintaining adequate nutrient intake. Several alternatives to CR exist. CR combined with exercise (CE) consists of both decreased caloric intake and increased caloric expenditure. Alternate-day fasting (ADF) consists of two interchanging days; one day, subjects may consume food ad libitum (sometimes equaling twice the normal intake); on the other day, food is reduced or withheld altogether. Dietary restriction (DR) - restriction of one or more components of intake (typically macronutrients) with minimal to no reduction in total caloric intake - is another alternative to CR. Many religions incorporate one or more forms of food restriction. The following religious fasting periods are featured in this review: 1) Islamic Ramadan; 2) the three principal fasting periods of Greek Orthodox Christianity (Nativity, Lent, and the Assumption); and 3) the Biblical-based Daniel Fast. This review provides a summary of the current state of knowledge related to CR and DR. A specific section is provided that illustrates related work pertaining to religious forms of food restriction. Where available, studies involving both humans and animals are presented. The review includes suggestions for future research pertaining to the topics of discussion.

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Impact of caloric and dietary restriction regimens on markers of health and longevity in humans and animals: a summary of available findings

Background: Muslims fast from sunrise to sunset during the month of Ramadan, the 9th lunar month. The duration of fasting varies from 13 to 18 h/day. Fasting includes avoidance of d

Islamic fasting and health.

In this study, we conducted a meta-analysis of self-controlled cohort studies comparing body weights, blood levels of lipids and fasting blood glucose levels before and after Ramadan taking into account gender differences. Several databases were searched up to June 2012 for studies showing an effect of Ramadan fasting in healthy subjects, yielding 30 articles. The primary finding of this meta-analysis was that after Ramadan fasting, low-density lipoprotein (SMD = -1.67, 95 % CI = -2.48 to -0.86) and fasting blood glucose levels (SMD = -1.10, 95 % CI = -1.62 to -0.58) were decreased in both sex groups and also in the entire group compared to levels prior to Ramadan. In addition, in the female subgroup, body weight (SMD = -0.04, 95 % CI = -0.20, 0.12), total cholesterol (SMD = 0.05, 95 % CI = -0.51 to 0.60), and triglyceride levels (SMD = 0.03, 95 % CI = -0.31, 0.36) remained unchanged, while HDL levels (SMD = 0.86, 95 % CI = 0.11 to 1.61, p = 0.03) were increased. In males, Ramadan fasting resulted in weight loss (SMD = -0.24, 95 % CI = -0.36, -0.12, p = 0.001). Also, a substantial reduction in total cholesterol (SMD = -0.44, 95 % CI = -0.77 to -0.11) and LDL levels (SMD = -2.22, 95 % CI = -3.47 to -0.96) and a small decrease in triglyceride levels (SMD = -0.35, 95 % CI = -0.67 to -0.02) were observed in males. In conclusion, by looking at this data, it is evident that Ramadan fasting can effectively change body weight and some biochemical parameters in healthy subjects especially in males compared to pre-Ramadan period.

N Khamaysi

Papers

Marked increase in plasma high-density-lipoprotein cholesterol after prolonged fasting during Ramadan.