A molecular clock exists within almost all organizations in a living body, and these clocks influence the periodicity of many physiological phenomena such as eating behaviors, the sleep-wake cycle, and hormone secretion. Especially, a living body's energy metabolism is involved with the molecular clocks genetically driven in peripheral tissues, which act in strong relation to eating rhythms. However, the possibility that rhythms may also have an inverse influence has recently been pointed out. In this manuscript, we review the outline of circadian rhythms, then refer to the possibility that a clock gene in the peripheral tissues, capable of being changed by eating rhythms, may influence sleep-wake regulation and energy metabolism.
Keywords: circadian rhythm; metabolism; sleep.