SYSTEMATIC REVIEWS AND META-ANALYSES The impact of Ramadan fasting on the metabolic syndrome severity in relation to ethnicity and sex: Results of a systematic review and meta-analysis Haitham Jahrami a,b, *, Khaled Trabelsi c,d , Omar A. Alhaj e , Zahra Saif a , Seithikurippu R. Pandi-Perumal f,g , Ahmed S. BaHammam h,i a Ministry of Health, Manama, Bahrain b Department of Psychiatry, College of Medicine and Medical Sciences, Arabian Gulf University, Manama, Bahrain c High Institute of Sport and Physical Education of Sfax, University of Sfax, Sfax 3000, Tunisia d Research Laboratory: Education, Motricity, Sport and Health, EM2S, LR19JS01, University of Sfax, Sfax 3000, Tunisia e Department of Nutrition, Faculty of Pharmacy and Medical Sciences, University of Petra, Amman, Jordan f Somnogen Canada Inc., College Street, Toronto, Canada g Saveetha Medical College and Hospitals, Saveetha Institute of Medical and Technical Sciences, Saveetha University, Chennai, Tamil Nadu, India h The Strategic Technologies Program of the National Plan for Sciences and Technologyand Innovation in the Kingdom of Saudi Arabia, Riyadh, Saudi Arabia i Department of Medicine, University Sleep Disorders Center and Pulmonary Service, King Saud University, Riyadh, KSA6, Saudi Arabia Received 14 May 2022; received in revised form 30 August 2022; accepted 5 September 2022 Handling Editor: A. Siani Available online --- KEYWORDS Cardiometabolic syndrome; Insulin resistance syndrome X; Intermittent fasting (IF); Metabolism; Reaven syndrome X; Time-restricted eating (TRE) Abstract Aims: The primary goal of this meta-analysis was to examine the changes in various components of metabolic syndrome (MetS) in healthy adults who observed Ramadan fasting (RF) before Ramadan (T1) and at the end of RF (T2). A secondary goal was to assess the impact of RF on MetS severity in various ethnic and sex groups using the MetS z-score. Data synthesis: Using PRISMA2020, seven databases were searched for relevant studies published between January 1950 and March 2022. Data extraction involved high-density lipoprotein cholesterol (HDL), triglycerides (TG), fasting blood glucose (FBG), waist circumference (WC), sys- tolic blood pressure (SBP), and diastolic blood pressure (DBP) for T1 and T2, respectively. The MetS z-score was computed according to international diabetes federation criteria. At T1, the pooled estimates of HDL, TG, FBG, WC, SBP, DBP, and MAP were 1.20 [1.13; 1.27] mmol/L,1.32 [1.23; 1.42] mmol/L, 4.98 [4.82; 5.15] mmol/L, 87.21 [84.21; 90.21] Cm,114.22 [101.45; 126.99] mmHg, 76.80 [70.12; 83.47] mmHg, and 89.27 [80.56; 97.98] mmHg, respectively. At T2, the pooled estimates of HDL, TG, FBG, WC, SBP, DBP, and MAP were 1.24 [1.18; 1.31] mmol/L,1.24 [1.14; 1.34] mmol/L, 4.77 [4.55; 4.99] mmol/L, 85.73 [82.83; 88.64] Cm, 109.48 [97.20; 121.75] mmHg, 74.43 [68.01; 80.85] mmHg, and 86.11 [77.74; 94.48] mmHg, respectively. The MetS z- score showed improvement at T2 for all ethnic groups and both sexes by 0.22 [-0.24; 0.01]. Conclusions: The current meta-analysis suggests that the RF positively impact the MetS compo- nents and the overall MetS z-score. PROSPERO registration number: ID CRD42022329297 Open Science Framework Identifier: DOI 10.17605/OSF.IO/U9H7T ª 2022 The Italian Diabetes Society, the Italian Society for the Study of Atherosclerosis, the Ital- ian Society of Human Nutrition and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved. * Corresponding author. College of Medicine and Medical Sciences, Department of Psychiatry, Arabian Gulf University, Bahrain. E-mail addresses: hjahrami@health.gov.bh (H. Jahrami), trabelsikhaled@gmail.com (K. Trabelsi), omar.alhaj@uop.edu.jo (O.A. Alhaj), zsaif@health. gov.bh (Z. Saif), pandiperumal2021@gmail.com (S.R. Pandi-Perumal), ashammam2@gmail.com (A.S. BaHammam). Please cite this article as: Jahrami H et al., The impact of Ramadan fasting on the metabolic syndrome severity in relation to ethnicity and sex: Results of a systematic review and meta-analysis, Nutrition, Metabolism & Cardiovascular Diseases, https://doi.org/10.1016/ j.numecd.2022.09.001 https://doi.org/10.1016/j.numecd.2022.09.001 0939-4753/ª 2022 The Italian Diabetes Society, the Italian Society for the Study of Atherosclerosis, the Italian Society of Human Nutrition and the Department of Clinical Medicine and Surgery, Federico II University. Published by Elsevier B.V. All rights reserved. Nutrition, Metabolism & Cardiovascular Diseases (xxxx) xxx, xxx Available online at www.sciencedirect.com Nutrition, Metabolism & Cardiovascular Diseases journal homepage: www.elsevier.com/locate/nmcd