Impact of Ramadan Diurnal Intermittent Fasting on Metabolic Syndrome Components in Healthy, Non-Athletic Muslim People Aged Over 15 Years: A Systematic Review and Meta-Analysis.

Studies on the impact of Ramadan diurnal intermittent fasting (RDIF) on metabolic syndrome (MetS) components among healthy Muslims observing Ramadan month have yielded contradictory results. This comprehensive meta-analysis aimed to obtain a more stable estimate of the effect size of fasting during Ramadan on MetS components, examine variability among studies, assess the generalizability of reported results, and perform subgroup analyses for associated factors. We searched the CINAHL, Cochrane, EBSCOhost, Google Scholar, ProQuest Medical, PubMed/MEDLINE, ScienceDirect, Scopus, and Web of Science databases for relevant studies published from 1950 to March, 2019. The MetS components analyzed were: waist circumference (WC), systolic blood pressure (SBP), fasting plasma/serum glucose (FG), triglycerides (TG), and high-density lipoprotein (HDL) cholesterol. We identified 85 studies (4,326 participants in total) that were conducted in 23 countries between 1982 and 2019. RDIF-induced effect sizes for MetS components were: small reductions in WC (no. of studies K=24, N=1,557, Hedge's g=-0.312, 95% confidence interval [CI]: -0.387 to -0.236), SBP (K=22, N=1,172, Hedge's g=-0.239, 95% CI: -0.372 to -0.106), FG (K=51, N=2,318, Hedge's g=-0.101, 95% CI: -0.260 to 0.004), and TG (K=63, N=2,862, Hedge's g=-0.088, 95% CI: -0.171 to -0.004), and a small increase in HDL cholesterol (K=57, N=2,771, Hedge's g=0.150, 95% CI: 0.064 to 0.236). We concluded that among healthy people, RDIF shows small improvement in the five MetS components: WC, SBP, TG, FG and HDL..