The impact of a western diet on gut microbiota and circadian rhythm: A comprehensive systematic review of in vivo preclinical evidence

Aims: Here, we present a systematic review that compiles in vivo experimental data regarding the effect of the WD on the gut microbiota and its impact on the circadian rhythm. Additionally, we reviewed studies evaluating the combined effects of WD and circadian cycle disruption on gut microbiota and circadian cycle markers. Materials and methods: The original studies indexed in PubMed/Medline, Scopus, and Web of Science databases were screened according to the PRISMA strategy. Key findings: Preclinical studies revealed that WD triggers circadian rhythmicity disruption, reduces the alphadiversity of the microbiota and favors the growth of bacterial groups that are detrimental to intestinal homeostasis, such as Clostridaceae , Enterococcus , Parasutterella and Proteobacteria . When the WD is combined with circadian clock disruption, gut dysbiosis become more pronounced. Reduced cycling of Per3, Rev-erb and CLOCK in the intestine, which are related to dysregulation of lipid metabolism and potential metabolic disease, was observed. Significance: In conclusion, current evidence supports the potential of WD to trigger microbiota dysregulation, disrupt the biological clock, and increase susceptibility to metabolic disorders and potentially chronic diseases.