Nightshift work is associated with adverse health outcomes, which may be related to eating during the biological night, when circadian rhythms and food intake are misaligned. Nurses often undertake nightshift work, and we aimed to investigate patterns of energy distribution and dietary intake across 14 days in 20 UK National Health Service (NHS) nurses working rotational shifts. We hypothesised that the proportion of daily energy consumed during the nightshift would increase over consecutive nights. Primary and secondary outcome measures included intakes of energy and macronutrients. Our results show that nurses consumed the same total daily energy on nightshifts and non-nightshifts, but redistributed energy to the nightshift period in increasing proportions with a significant difference between Night 1 and 2 in the proportion of total daily energy consumed (26.0 ± 15.7% vs. 33.5 ± 20.2%, mean ± SD; p < 0.01). This finding indicates that, rather than increasing total energy intake, nurses redistribute energy consumed during nightshifts as a behavioural response to consecutive nightshifts. This finding informs our understanding of how the intake of energy during the biological night can influence adverse health outcomes of nightshift work.
Keywords: circadian misalignment; circadian rhythms; diet; nutrition; shift work.