Elsevier

Nutrition

Volume 35, March 2017, Pages 14-20
Nutrition

Review
Unraveling the metabolic health benefits of fasting related to religious beliefs: A narrative review

https://doi.org/10.1016/j.nut.2016.10.005Get rights and content

Highlights

  • Religious fasting reflects dietary habits of millions of believers.

  • Health impact of religious fasting has been documented among Buddhists, Christians, and Muslims.

  • Energy and/or food item restrictions are key components of religious fasting.

  • Religious fasting has potential benefits on energy balance, dyslipidemia and oxidative stress.

  • Religious fasting could be integrated into health management for diseases prevention.

Abstract

Periodic fasting, under a religious aspect, has been adopted by humans for centuries as a crucial pathway of spiritual purification. Caloric restriction, with or without exclusion of certain types of food, is often a key component. Fasting varies significantly among different populations according to cultural habits and local climate conditions. Religious fasting in terms of patterns (continuous versus intermittent) and duration can vary from 1 to 200 d; thus, the positive and negative impact on health can be considerable. Advantages of religious fasting are claimed by many but have been explored mainly by a limited number of studies conducted in Buddhist, Christian, or Muslim populations. These trials indicate that religious fasting has beneficial effects on body weight and glycemia, cardiometabolic risk markers, and oxidative stress parameters. Animals exposed to a diet mimicking fasting have demonstrated weight loss as well as lowered plasma levels of glucose, triacylglycerols, and insulin growth factor-1, although lean body mass remained stable. Diabetic mice on repeated intermittent fasting had less insulin resistance that mice fed ad libitum. The long-term significance of such changes on global health remains to be explored. This review summarizes the data available with regard to benefits of fasting followed for religious reasons on human health, body anthropometry, and cardio-metabolic risk markers; aims to bridge the current knowledge gap on available evidence and suggests considerations for the future research agenda. Future studies should explore every type of religious fasting, as well as their consequences in subpopulations such as children, pregnant women, and the elderly, or patients with chronic metabolic diseases.

Introduction

Various forms of fasting have been used for health and for religious reasons for centuries. Fasting is defined as the abstinence from food for varying duration, and has been associated with increased longevity and a potential beneficial role for human health [1]. Fasting tends to be a dietary habit among people in the context of a health-promoting dietary pattern [2]. Religious fasting (RF) is primarily based on various levels of caloric restriction and limitations of food items, and comprises an essential feature in most popular religions [1]. From a spiritual point of view, RF aims at the purgation of the soul and body. Following RF as a dietary pattern is considered as a means to attain high spiritual virtues [1], [3]. Although exact mechanisms of its role on human health remain unclear, previous results indicated potential beneficial effects, including prevention of certain diseases such as obesity, diabetes mellitus type 2, and cardiovascular diseases [3], [4]. Religious fasting has gained popularity outside of countries of origin as a consequence of the migration of population. Healthcare personnel may have limited knowledge about RF and its relevance in the management of health. The benefits of RF on human health are based on a limited body of evidence. The results of animal experiments have been used to support some of the claims.

This review aims at summarizing available evidence regarding potential protective effects of fasting followed for religious reasons on human health, body anthropometry, and cardio-metabolic risk markers, with an analysis of the current knowledge gap from available evidence and with the future research agenda in mind.

Section snippets

Criteria of selected fasting models

The literature search was performed on PubMed, Scopus, Google scholar, and Google using three keywords: “fasting,” “religious fasting,” and “intermittent fasting.” The results are summarized in Figure 1. We did not report the specific impact of fasting on metabolism or health when no scientific data were found. For example, although Hindu fasting is followed by millions of believers, the characteristics of fasting are not consistent, and therefore, it is impossible to draw meaningful

Effects of fasting in animals

Animal trials indicate beneficial effects of intermittent fasting (no food intake versus ad libitum intake) on health [6]. Brandhorst et al. studied 110 mice (C57 Bl/6) consuming a mimicking fasting diet for 4 d twice per month for 6 mo [8]. Control group of mice was fed daily ad libitum (15.7 KJ/g body weight). Fasting was divided in day 1 (7.7 KJ/g body weight) and day 2 to 4 (1.5 KJ/g body weight) [8]. Mice had lost weight (15% of the baseline body weight), reduced glycemia (40%) and insulin

Effects of fasting on human health

The impact of fasting for non-religious reasons has been extensively studied in healthy and diseased humans [29], [30], [31], [32]. The differential effects of short versus long, partial versus complete fasting, with or without stress-related acute or chronic diseases have been reviewed in details elsewhere [32], [33], [34]. Fasting to modify body reaction to conventional treatment (e.g., cancer and inflammation) has gained popularity but remains mostly poorly explored [6], [33], [34]. This

Effects of Ramadan fasting on human health

Numerous observational studies on Ramadan fasting are available, but with variable effects on human health. A meta- analysis examining the effect of Ramadan fasting on body weight and energy intake included 35 prospective studies in their final analysis [25]. A significant trend toward weight loss was evident in most studies (−1.24 kg; 95% CI: −0.88 to 1.60, P < 0.001) during Ramadan fasting, followed by a significant BW increase after the fasting period (+0.72 kg; 95% CI: 0.32 to 1.13, P

Conclusions

Available evidence suggests beneficial effects of RF on human health, although it relies on small, unblinded, and uncontrolled studies. Future studies should explore every type of RF, as well as subpopulations such as children, pregnant women and the elderly, or patients with chronic metabolic diseases. We also need a better understanding of the mechanisms by which RF affects metabolism. Finally, as RF becomes more and more popular, it would be advisable to integrate RF dietary patterns into

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    No conflicts of interest are declared. The authors thank Professors M.M. Berger, C. Dibner, J. Jaafar, and P. Singer for their comments and suggestions to improve the manuscript.

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