The study investigates the impact of a mutation in the *Clock* gene, which encodes a bHLH-PAS transcription factor, on circadian rhythms and metabolic health in mice. Homozygous *Clock* mutant mice exhibit attenuated diurnal feeding rhythms, increased food intake, and obesity. These mice also develop a metabolic syndrome characterized by hyperleptinemia, hyperlipidemia, hepatic steatosis, and hyperglycemia, with insufficient insulin production, a hallmark of type 2 diabetes. The expression of hypothalamic peptides involved in energy balance is significantly reduced in *Clock* mutant animals. These findings suggest that the circadian clock gene network plays a crucial role in mammalian energy balance, affecting multiple tissues and leading to obesity and metabolic syndrome when disrupted. The study highlights the importance of circadian rhythms in regulating metabolic processes and provides a genetic model to explore the complex interactions between the circadian clock, behavior, and metabolism.The study investigates the impact of a mutation in the *Clock* gene, which encodes a bHLH-PAS transcription factor, on circadian rhythms and metabolic health in mice. Homozygous *Clock* mutant mice exhibit attenuated diurnal feeding rhythms, increased food intake, and obesity. These mice also develop a metabolic syndrome characterized by hyperleptinemia, hyperlipidemia, hepatic steatosis, and hyperglycemia, with insufficient insulin production, a hallmark of type 2 diabetes. The expression of hypothalamic peptides involved in energy balance is significantly reduced in *Clock* mutant animals. These findings suggest that the circadian clock gene network plays a crucial role in mammalian energy balance, affecting multiple tissues and leading to obesity and metabolic syndrome when disrupted. The study highlights the importance of circadian rhythms in regulating metabolic processes and provides a genetic model to explore the complex interactions between the circadian clock, behavior, and metabolism.