Circadian clocks time the daily occurrence of multiple aspects of behaviour and physiology. Through studies of chronic misalignment between our internal clocks and the environment (e.g. during shift work), it has long been postulated that disruption of circadian rhythms is detrimental to human health. Recent advances in understanding of the cellular and molecular basis of mammalian circadian timing mechanisms have identified many key genes involved in circadian rhythm generation and demonstrated the presence of clocks throughout the body. Furthermore, clear links between sleep, circadian rhythms and metabolic function have been revealed, and much current research is studying these links in more detail. Here, we review the evidence linking circadian rhythms, clock genes and adipose biology. We also highlight gaps in our understanding and finally suggest avenues for future research.