The article reviews the integration of metabolism and circadian rhythms, highlighting the role of circadian clocks in coordinating metabolic functions with the day/night cycle. Circadian clocks, present in nearly all vertebrate cells, align with the endogenous environment and are regulated by genetic factors. Disruption of these clocks, often seen in shift work and sleep deprivation, leads to metabolic disorders such as obesity and diabetes. The review discusses the core transcriptional components of the circadian clock, including the CLOCK-BMAL1 complex and the PER and CRY proteins, and their post-translational regulation by casein kinases and AMP kinase. It also explores the crosstalk between the clock and metabolic transcription networks, particularly the involvement of nuclear hormone receptors (NHRs) like REV-ERBα and PPARα in metabolic gene regulation. The article further examines how circadian disruption causes metabolic pathologies, including the impact on bile acid synthesis, lipogenesis, cardiovascular function, inflammation, and glucose homeostasis. Finally, it discusses the relationship between sleep and circadian disruption, and the potential therapeutic implications of understanding these interconnections.The article reviews the integration of metabolism and circadian rhythms, highlighting the role of circadian clocks in coordinating metabolic functions with the day/night cycle. Circadian clocks, present in nearly all vertebrate cells, align with the endogenous environment and are regulated by genetic factors. Disruption of these clocks, often seen in shift work and sleep deprivation, leads to metabolic disorders such as obesity and diabetes. The review discusses the core transcriptional components of the circadian clock, including the CLOCK-BMAL1 complex and the PER and CRY proteins, and their post-translational regulation by casein kinases and AMP kinase. It also explores the crosstalk between the clock and metabolic transcription networks, particularly the involvement of nuclear hormone receptors (NHRs) like REV-ERBα and PPARα in metabolic gene regulation. The article further examines how circadian disruption causes metabolic pathologies, including the impact on bile acid synthesis, lipogenesis, cardiovascular function, inflammation, and glucose homeostasis. Finally, it discusses the relationship between sleep and circadian disruption, and the potential therapeutic implications of understanding these interconnections.