Abstract
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.
Highlights
Since the seminal work of McCay et al [1], much interest has been shown in caloric restriction’s ability to improve health and to extend lifespan
While Caloric restriction (CR) reduces caloric intake, CR combined with exercise (CE) both reduces caloric intake and increases caloric expenditure
In an attempt to determine the optimal plan for improved health, future work may investigate varying amounts of exercise-induced caloric expenditure coupled with varying amounts of decreased caloric intake
Summary
Since the seminal work of McCay et al [1], much interest has been shown in caloric restriction’s ability to improve health and to extend lifespan. Several studies have found that increasing intake either increases or has no effect on longevity, suggesting that restriction would not extend life [28,29], reviewed in [30] Both forms of macronutrient restriction fail to decrease reactive oxygen species production or oxidative DNA damage [31,32]. There are several potential confounding variables that may influence the effect of Ramadan fasting on these biomarkers, including: age, physical activity, diet, sleep cycles, and cultural habits [126,150] Regarding the latter, El-Ati et al [126] reported that total energy intake increased among Saudi subjects and decreased among Indian subjects during Ramadan, and that this discrepancy was due to the differences in food choices between the two groups.
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