A Greek word for nice or beautiful, ‘oreo’ (ωραίο), which literally means ‘something happening at the correct hour’ (ώρα), underscores the importance of living in a ‘timely’ way. Our body’s internal circadian timing system regulates many aspects of our physiology and behaviour over a 24-hour period and works best when aligned with the sleep–wake cycle.

Mistimed lifestyle conditions (including jet lag, social jet lag and night shift work) are becoming more common and have been associated with an increased risk of developing cardiovascular diseases, diabetes mellitus and obesity. However, the pathophysiological background has not been fully understood despite clear observational data.