Social jetlag predicts greater evening energy intake in a UK cohort.

Social jetlag describes the differences in sleep timing between workdays and weekends. In a 14-day longitudinal observational study, we explored the associations between social jetlag and energy intake on workdays and weekends. Healthy male and female participants residing in the UK [n = 101] used a smartphone app to record dietary intake continuously during the study period, encompassing two working weeks and weekends. We hypothesised that higher social jetlag levels would be associated with greater evening energy intake. Using regression models with complementary social jetlag classifications, we found that increasing social jetlag levels modified temporal energy intake in both female and male participants. Overall, participants with less social jetlag exhibited earlier energy intake, while participants with more social jetlag exhibited later energy intake, although the modifying effect of social jetlag differed slightly between weekdays and weekends and the sexes. Importantly, however, the magnitude of the effect estimates was modest and, in caloric terms, unlikely to explain the higher risks of obesity and metabolic diseases previously associated with increasing social jetlag levels.