Effects of Intermittent Fasting on Regulation of Metabolic Homeostasis: A Systematic Review and Meta-Analysis in Health and Metabolic-Related Disorders

Advancing Chrononutrition for Cardiometabolic Health: A 2023 National Heart, Lung, and Blood Institute Workshop Report

The circadian system maintains optimal biological functions at the appropriate time of day, and the disruption of this organization can contribute to the pathogenesis of cardiometabolic disorders. The timing of eating is a prominent external time cue that influences the circadian system. "Chrononutrition" is an emerging dimension of nutrition and active area of research that examines how timing-related aspects of eating and nutrition impact circadian rhythms, biological processes, and disease pathogenesis. There is evidence to support chrononutrition as a form of chronotherapy, such that optimizing the timing of eating may serve as an actionable strategy to improve cardiometabolic health. This report summarizes key information from the National Heart, Lung, and Blood Institute's virtual workshop entitled "Chrononutrition: Elucidating the Role of Circadian Biology and Meal Timing in Cardiometabolic Health," which convened on May 2 to 3, 2023, to review current literature and identify critical knowledge gaps and research opportunities. The speakers presented evidence highlighting the impact on cardiometabolic health of earlier and shorter eating windows and more consistent day-to-day eating patterns. The multidimensionality of chrononutrition was a common theme, as it encompasses multiple facets of eating along with the timing of other behaviors including sleep and physical activity. Advancing the emerging field of chrononutrition will require: (1) standardization of terminology and metrics; (2) scalable and precise tools for real-world settings; (3) consideration of individual differences that may act as effect modifiers; and (4) deeper understanding of social, behavioral, and cultural influences. Ultimately, there is great potential for circadian-based dietary interventions to improve cardiometabolic health.

The Effect of Intermittent Fasting on Salivary Inflammatory Cytokines and Dopamine Levels

OBJECTIVES

 The current study elucidates potential alterations in inflammatory cytokines and dopamine (DA) levels in saliva following a 21-day fasting regimen during Ramadan and explores their associations with mental health parameters.

MATERIALS AND METHODS

 Forty-four healthy young university students (22 females and 22 males; median age 22 (2) and body mass index 23.40 (6.23) were enrolled, and saliva samples were collected before and after fasting. Cytokine and DA levels were quantified by ELISA and LEGENDplex Human Inflammation Panel, respectively. Participants also completed the Patient Health Questionnaire-9 and Depression Anxiety Stress Scales questionnaires to assess mental health.

STATISTICAL ANALYSIS

 Data analysis was performed using SPSS. Differences between pre- and postfasting were tested using Wilcoxon's signed-rank test. Mann-Whitney's U test determined disparities in DA and cytokine levels across sex. Simple and multiple linear regression analyses were performed to identify the factors influencing the change in DA. Correlation analysis was employed to explore the relationships between the changes in DA and cytokine levels before and after fasting.

RESULTS

 A significant increase in inflammatory cytokines such as interleukin (IL)-1β, interferon-α2, tumor necrosis factor-α, IL-23, IL-33, and IL-8 was observed after fasting. Anti-inflammatory cytokine, IL-10, levels remained unchanged. Females had significantly higher levels of proinflammatory cytokines before fasting compared with males, but no significant gender differences were observed after fasting. The current study also showed a significant decrease in DA levels after fasting; however, no significant difference in DA levels across genders was noted. Self-reported mental health status did not significantly change before and after fasting. Multiple linear regression analyses did not suggest potential associations between these variables and changes in DA levels before and after fasting. However, correlation analysis indicated that the change in inflammatory cytokine levels was inversely related to changes in DA levels.

CONCLUSION

 Fasting during Ramadan significantly increased salivary cytokine levels and decreased DA levels, indicating potential relationships between immune factors and mental well-being. The findings highlight the complex interplay between inflammation, immunity, and DA regulation during fasting. Further research is warranted to elucidate the potential long-term effects of these associations and their implications for mental health and well-being.

Body Weight Changes During Ramadan Intermittent Fasting: A Cross-Sectional Study of Healthy Adults in Turkey

Introduction: This study explores the impact of observing Ramadan intermittent fasting (RIF) on body weight in Turkish residents, marking it as the first study conducted in Turkey to investigate the interplay of religious fasting with dietary changes amid the COVID-19 pandemic. We hypothesized that observing Ramadan fasting would result in weight loss attributable to dietary changes, while decreased physical activity would correlate with weight gain during this period. Methods: A cross-sectional survey was conducted among Muslims aged 18+ in Turkey who fasted at least two days during Ramadan 2021. Data were collected via Google Forms, with 1669 participants recruited through social media. Descriptive statistics summarized participant characteristics, and Pearson's Chi-square tests assessed weight change differences. Binary logistic regression identified predictors of weight gain, adjusting for factors such as sex, age, physical activity, water consumption, and diet. Results: Of the 1669 respondents (53.6% female), 49.4% perceived their weight as normal, while 47.0% classified themselves as overweight or obese. Logistic regression indicated that decreased physical activity (AOR = 1.618, p=0.001) and increased fat intake (AOR = 1.9, 95% CI 1.2-2.9) were significant predictors of weight gain. Conclusion: Our findings emphasize the importance of promoting healthy eating and regular physical activity during Ramadan.

Intermittent fasting as a treatment for obesity in young people: a scoping review

Intermittent fasting focuses on the timing of eating rather than diet quality or energy intake, with evidence supporting its effects on weight loss and improvements in cardiometabolic outcomes in adults with obesity. However, there is limited evidence for its feasibility and efficacy in young people. To address this, a scoping review was conducted to examine intermittent fasting regimens in individuals aged 10 to 25 for the treatment of obesity focusing on methodology, intervention parameters, outcomes, adherence, feasibility, and efficacy. Due to the paucity of evidence in this age group, to adequately assess feasibility and adherence, all published studies of intermittent fasting in this age category, regardless of weight status and treatment intention, were included in the review. The review included 34 studies (28 interventional studies and 6 observational studies) with 893 participants aged 12 to 25. Interventions varied with 9 studies in cohorts with obesity utilizing intermittent fasting as an obesity treatment. Thirteen studies utilized 8-h time-restricted eating. Primary outcomes included cardiometabolic risk factors (7/28), anthropometric measurements (7/28), body composition (5/28), muscular performance (4/28), feasibility (1/28), and others (4/28). All 9 studies conducted in young people with obesity reported some degree of weight loss, although the comparator groups varied significantly. This review underscores the various utilizations of intermittent fasting in this age group and highlights its potential in treating obesity. However, the findings emphasize the need for rigorous studies with standardized frameworks for feasibility to ensure comparability and determine intermittent fasting's practicality in this age group depending on the treatment outcome of interest.

Fasting recovers age-related hypertension in the rats: reset of renal renin-angiotensin system components and klotho

BACKGROUND

The renal renin-angiotensin system (RAS) plays a vital part in the control of blood pressure and is known to be affected by aging. This study aimed to investigate the effects of intermittent fasting on age-related hypertension and the expression of local renal RAS components.

METHODS

The Wistar rats were categorized into three main age groups (young, middle aged, and elderly) and three dietary treatment models, including ad libitum feeding (AL), every other day fasting (EOD), and one day per week of fasting (FW). After three months, blood pressure (BP) was assessed. Some genes and proteins of the renal RAS system were measured by using Real time PCR and Western blot. α-klotho and Ang II proteins were assessed by ELISA method.

RESULTS

Old rats exhibited significantly increase in BP and Ang II (P < 0.001 vs. young rats) and a significant reduction in circulating levels of α-klotho and kidney AT2R protein (P < 0.001, P < 0.01, vs. young rats, respectively). Additionally, they respond to aging by increasing the AT1aR/AT2R proteins ratio (P < 0.05). Two model of feeding reduced BP in old rats and circulating Ang II in middle-aged and older rats. Moreover, by fasting, ACE2 protein expression was elevated in old rats. EOD fasting also significantly elevated the AT2 receptor protein and reduced the AT1aR/AT2R proteins ratio in the older rats (P < 0.001, P < 0.01, respectively).

CONCLUSION

Our findings suggest that fasting, particularly EOD, can attenuate age-related hypertension, partly through reset of the local renal RAS and increase of klotho protein expression.

Mediterranean diet and spirituality/religion: eating with meaning

The interest in the Mediterranean diet has grown considerably due to its potential health benefits on the prevention of diverse age-related chronic diseases and its association with longevity. This dietary pattern, considered among the healthiest in the world, is not simply a combination of healthy foods but goes further in its historical and cultural roots. Mediterranean diet is not intrinsically tied to any specific religion or spiritual system, but its cultural and geographical context has influenced the dietary practices of its inhabitants, encompassing the history of Western civilization and of the three Monotheistic religions Christianity, Judaism, and Islam. These religions may have some impact on dietary choices due to religious customs and practices. In 2010 the Mediterranean diet was inscribed on the UNESCO's Representative List of Intangible Cultural Heritage of Humanity, highlighting it as a social and cultural expression of the different food cultures of the Mediterranean region and indicating that the importance of this dietary and lifestyle pattern lies not only in its specific foods and nutrients, but in the way in which its characteristic foods are produced, cooked, and eaten. In this narrative review we will discuss the possible connections between the main religions originated in the Mediterranean basin and their influence on the composition of the Mediterranean diet, and the links between spirituality/religion and this dietary pattern. This traditional model can represent a form of conscious healthy eating and lifestyle in contrast to the unhealthy Western lifestyle and ultra-processed food consumption widespread throughout the world.

Effect of fasting-induced headache on calcitonin gene related peptide (CGRP) and other clinical biomarkers on the first day of Ramadan: Sub-analysis from a randomized open label clinical trial

BACKGROUND

Fasting-induced headaches (FIHs) have been shown to occur on the first day of Ramadan and clearly decline thereafter. Despite the wealth of knowledge about different types of headaches (e.g., migraine-, cluster-, and tension-type headaches), research on the mechanism underlying FIHs, as well as their treatment, remains scarce. Our study aimed to investigate any association between FIHs during the first day of Ramadan and potential headache-related biomarkers, including fasting blood glucose (FBG), C-reactive protein (CRP), magnesium, vitamin B9, vitamin B12, homocysteine, and calcitonin gene related peptide (CGRP), and to assess whether a prophylactic use of paracetamol may influence these biomarkers.

METHODS

As part of a randomized, open-label clinical trial that evaluated the effect of paracetamol as a prophylactic therapy for FIH, blood samples from stratified subjects in the prophylaxis and control groups were withdrawn while fasting after the 1st dose of paracetamol (in the prophylaxis group) and prior to reporting headache occurrence.

RESULTS

Plasma and serum were separated for 61 subjects; 31 and 30 subjects from the prophylaxis and control groups, respectively. Overall, no significant differences were found in the levels of FBG, CRP, magnesium, vitamin B9, and vitamin B12 in headache-suffering subjects compared to those without headache despite the use of paracetamol for prophylaxis. Homocysteine, however, was significantly reduced in all subjects who experienced FIH compared to those without headache (median 6.9 [1.6] vs. 7.7 [2.7] umol/L; p = 0.041). On the contrary, when the CGRP was measured using immunoassay, it was found to be significantly elevated in all headache-suffering subjects compared to those without headache (median 126.1 [17.7] vs. 105.8 [19.6] pg/mL; p ≤ 0.0001). This difference was maintained upon comparing the headache to non-headache subjects in both the prophylaxis (median 121.5 [15.4] vs. 105.8 [9.4] pg/mL; p < 0.01) and control groups (median 128.5 [28.3] vs. 105.8 [23.8] pg/mL; p < 0.01). Additionally, an elevated CGRP level was found to increase the odds of having a FIH [OR = 1.32; 95%CI 1.06-1.22].

CONCLUSIONS

Our findings revealed the role of CGRP in FIHs for the first time and suggest further investigation in signaling pathways downstream CGRP receptors. Furthermore, the modulation CGRP or CGRP receptors could have a clinical application in the prevention of FIHs.

TRIAL REGISTRATION

This study was registered with the Saudi Food and Drug Authority in the Saudi Clinical Trials Registry (SCTR; No. 22122102).

Therapeutic Potential of Various Intermittent Fasting Regimens in Alleviating Type 2 Diabetes Mellitus and Prediabetes: A Narrative Review

Intermittent fasting has drawn significant interest in the clinical research community due to its potential to address metabolic complications such as obesity and type 2 diabetes mellitus. Various intermittent fasting regimens include alternate-day fasting (24 h of fasting followed by 24 h of eating), time-restricted fasting (fasting for 14 h and eating within a 10 h window), and the 5:2 diet (fasting for two days and eating normally for the other five days). Intermittent fasting is associated with a reduced risk of type 2 diabetes mellitus-related complications and can slow their progression. The increasing global prevalence of type 2 diabetes mellitus highlights the importance of early management. Since prediabetes is a precursor to type 2 diabetes mellitus, understanding its progression is essential. However, the long-term effects of intermittent fasting on prediabetes are not yet well understood. Therefore, this review aims to comprehensively compile existing knowledge on the therapeutic effects of intermittent fasting in managing type 2 diabetes mellitus and prediabetes.

Reply to Dietvorst et al. Challenges in Providing an Overview of Results of Intermittent Fasting Interventions on Diabetes Parameters. Comment on "Silva et al. Effects of Intermittent Fasting on Regulation of Metabolic Homeostasis: A Systematic Review and Meta-Analysis in Health and Metabolic-Related Disorders. J. Clin. Med. 2023, 12, 3699"

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Challenges in Providing an Overview of Results of Intermittent Fasting Interventions on Diabetes Parameters. Comment on Silva et al. Effects of Intermittent Fasting on Regulation of Metabolic Homeostasis: A Systematic Review and Meta-Analysis in Health and Metabolic-Related Disorders. J. Clin. Med. 2023, 12, 3699

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Intermittent Fasting in Youth: A Scoping Review

Intermittent fasting (IF) focuses on the timing of eating rather than diet quality or energy intake, with evidence supporting its effects on weight loss and cardiometabolic outcomes in adults. However, there is limited evidence for its efficacy in adolescents and emerging adults. To address this, a scoping review examined IF regimens in individuals aged 10 to 25, focusing on methodology, intervention parameters, outcomes, adherence, feasibility, and efficacy. The review included 39 studies with 731 participants aged 15 to 25. Methodologies varied, with 18 studies on time-restricted eating and others requiring caloric restriction. Primary outcomes included cardiometabolic risk factors (11/29), body composition (9/29), anthropometric measurements (8/29), and feasibility (2/29). Most studies reported significant weight loss. This review underscores IF's potential in treating obesity in this age group but highlights the need for rigorous studies with standardized frameworks for feasibility to ensure comparability and determine IF's practicality in this age group.

Chrononutrition in the Prevention and Management of Metabolic Disorders: A Literature Review

BACKGROUND

The concept of time-restricted eating (TRE) or time-restricted feeding (TRF) promotes daily periods of feeding and fasting to determine whole-body physiology. Chronic misalignment of circadian rhythms or chrono-disruption is related to an increased risk of diverse metabolic disorders. The progression of non-communicable diseases seems to be affected by the timing of meals. As a result, intermittent fasting is a promising approach for their management. The aim of the present literature review is to examine and scrutinize the TRE protocols in the fields of prevention and management of metabolic disorders.

METHODS

This is a thorough literature review of the reported associations among circadian rhythm, metabolic disorders, diabetes mellitus, obesity, TRE, TRF, dietary habits, circadian disruption, cardiovascular diseases, atherosclerosis, and non-alcoholic fatty liver to find the already existing clinical studies from the last decade (2014-2024) in the most precise scientific online databases, using relevant specific keywords. Several inclusion and exclusion criteria were applied to scrutinize only longitudinal, cross-sectional, descriptive, and prospective clinical human studies.

RESULTS

The currently available clinical findings remain scarce and suggest that chrononutrition behaviors such as TRE or TRF may promote several metabolic benefits, mainly in body weight control and fat loss. Improvements in glucose levels and lipid profiles are currently quite controversial since some clinical studies show little or no effect. As far as liver diseases are concerned, the efficacy of intermittent fasting seems to be stronger in the management of non-alcoholic fatty liver disease due to body weight decline and fat loss.

CONCLUSIONS

Even if there has been a gradual increase in clinical studies in the last few years, providing promising perspectives, currently, there is no conclusive evidence for the role of chrononutrition in metabolic disorders. Future studies should be well-designed with longer duration and larger sample sizes. Moreover, it is important to examine the best timing of the eating window and its feasibility.

Sociodemographic Factors Associated with Improved Metabolic Syndrome in Slum Dwelling Adults in Kenya: A Randomized Controlled Trial

Background

Sociodemographic factors have been implicated in cardiovascular health with differential morbidity and mortality. It is essential to comprehend how sociodemographic factors contribute to the improvement of Metabolic Syndrome (MetS), the primary cardiovascular diseases indicator.

Objective

Determine the role of sociodemographic factors in improving MetS among adults residing in the Slums of Nairobi, Kenya.

Methods

Adults with MetS participated in this randomized controlled trial study for a period of 12-months. A random assignment was used to place eligible participants in the intervention or control groups. The intervention group received lifestyle intervention that entails not using tobacco products or alcohol, exercising, and adhering to recommended dietary guidelines, while the control group had standard medical care. Clinical, biochemistry, and lifestyle habits were measured before and a year after the intervention. The association between the sociodemographic factors and the improvement in MetS was examined using a multiple logistic regression model with backward conditional.

Results

In the intervention group, lack of improvement in metabolic syndrome was significantly higher among aged (≥50 years) respondents [AOR = 9.097; P < .001]; Protestants [AOR = 7.292; P = .017] and Catholics [AOR = 5.270; P = .050]. Compared to unemployed, formally employed respondents had an 84.6% lower chance of having MetS [AOR = 0.154; P = .005]. Within the control group, lack of improvement in metabolic syndrome was significantly higher among aged (≥50 years) respondents [AOR = 5.013; P = .047]. Compared to respondents who had less than $100, individuals with monthly incomes between $100 and $500 had a roughly 10-fold [AOR = 10.499; P = .024] higher chance of having MetS.

Conclusion

In the current study, the findings show that sociodemographic factors namely: advanced age, unemployment, being Protestants and Catholics as well as higher income were negatively associated with improvement in MetS. The findings indicate that social factors have impact in the management and intervention outcomes of CVDs. Programmers and policy makers should plan interventions for CVD prevention and response with these factors in mind.

Diabesity and Dietary Interventions: Evaluating the Impact of Mediterranean Diet and Other Types of Diets on Obesity and Type 2 Diabetes Management

BACKGROUND

Diabesity, the intersection of obesity and diabetes, presents a global health crisis with profound implications. Addressing diabesity requires multifaceted strategies, with diet playing a pivotal role. Over the last 15 years, clinical studies have intensified their exploration of various dietary approaches in diabesity management. This literature review aims to synthesize findings from clinical studies conducted in the last 15 years, shedding light on the efficacy, mechanisms, and nuances of different diet types in diabesity management with special focus on the Mediterranean diet (MD).

METHODS

Thorough research of academic databases yielded a collection of relevant clinical studies. These studies encompassed a range of dietary strategies, including the MD, low-carbohydrate diets, plant-based diets, high-protein diets, low-fat regimens, and intermittent fasting. Key findings, methodologies, and outcomes were thoroughly extracted and analyzed.

RESULTS

The last 15 years have witnessed considerable improvements in recognizing the role of human nutritional habits in diabesity management. The MD appears to be the most well-recognized diet, exerting favorable effects against both obesity and diabetes. Low-carbohydrate diets were found to enhance glycemic regulation and decrease insulin resistance. Plant-based diets demonstrated potential benefits in weight management and cardiometabolic health. High-protein, low-fat dietary models exhibited positive effects on satiety and body weight decline. Intermittent fasting regimens also exerted metabolic improvements and body weight decline. Personalization emerged as a crucial factor in dietary recommendations.

CONCLUSIONS

Clinical studies from the last 15 years underscore the intricate relationship between diet types and diabesity management. The above results contribute to an increasing body of evidence, emphasizing the need for tailored dietary approaches and especially the MD. Healthcare providers can utilize this knowledge to offer personalized dietary recommendations for individuals with diabesity, potentially curbing the rise of these twin epidemics and improving the well-being of affected populations.

Understanding Type 2 Diabetes Mellitus Risk Parameters through Intermittent Fasting: A Machine Learning Approach

Type 2 diabetes mellitus (T2DM) is a chronic metabolic disorder characterized by elevated blood glucose levels. Despite the availability of pharmacological treatments, dietary plans, and exercise regimens, T2DM remains a significant global cause of mortality. As a result, there is an increasing interest in exploring lifestyle interventions, such as intermittent fasting (IF). This study aims to identify underlying patterns and principles for effectively improving T2DM risk parameters through IF. By analyzing data from multiple randomized clinical trials investigating various IF interventions in humans, a machine learning algorithm was employed to develop a personalized recommendation system. This system offers guidance tailored to pre-diabetic and diabetic individuals, suggesting the most suitable IF interventions to improve T2DM risk parameters. With a success rate of 95%, this recommendation system provides highly individualized advice, optimizing the benefits of IF for diverse population subgroups. The outcomes of this study lead us to conclude that weight is a crucial feature for females, while age plays a determining role for males in reducing glucose levels in blood. By revealing patterns in diabetes risk parameters among individuals, this study not only offers practical guidance but also sheds light on the underlying mechanisms of T2DM, contributing to a deeper understanding of this complex metabolic disorder.