A systematic review explores the connection between the gut microbiota and sleep disorders, as well as metabolic syndrome (MetS). The review highlights 36 studies linking gut microbial signatures with MetS or sleep disorders, focusing on dietary patterns, supplements, and probiotics. It concludes that dietary choices influence microbial composition and metabolites, affecting both MetS and sleep homeostasis. The gut microbiota interacts with the brain through the gut-brain axis, influencing sleep regulation and metabolic functions. Factors like diet, lifestyle, and environmental conditions affect the gut microbiome, which in turn impacts sleep and metabolic health. The review emphasizes the role of the gut microbiome in regulating circadian rhythms, immune responses, and metabolic pathways. It also discusses the impact of microbial metabolites on sleep quality and the potential of dietary interventions to improve gut microbiota composition and metabolic health. The review underscores the importance of a healthy diet in modulating the gut microbiome to enhance sleep and metabolic outcomes. The findings suggest that dietary patterns, such as the Mediterranean diet, can positively influence gut microbiota and improve sleep and metabolic parameters. The review concludes that further research is needed to validate these findings and understand the mechanisms underlying the gut-brain axis in MetS and sleep disorders.A systematic review explores the connection between the gut microbiota and sleep disorders, as well as metabolic syndrome (MetS). The review highlights 36 studies linking gut microbial signatures with MetS or sleep disorders, focusing on dietary patterns, supplements, and probiotics. It concludes that dietary choices influence microbial composition and metabolites, affecting both MetS and sleep homeostasis. The gut microbiota interacts with the brain through the gut-brain axis, influencing sleep regulation and metabolic functions. Factors like diet, lifestyle, and environmental conditions affect the gut microbiome, which in turn impacts sleep and metabolic health. The review emphasizes the role of the gut microbiome in regulating circadian rhythms, immune responses, and metabolic pathways. It also discusses the impact of microbial metabolites on sleep quality and the potential of dietary interventions to improve gut microbiota composition and metabolic health. The review underscores the importance of a healthy diet in modulating the gut microbiome to enhance sleep and metabolic outcomes. The findings suggest that dietary patterns, such as the Mediterranean diet, can positively influence gut microbiota and improve sleep and metabolic parameters. The review concludes that further research is needed to validate these findings and understand the mechanisms underlying the gut-brain axis in MetS and sleep disorders.