L. Kovacs, P. P. Ujma
Sleep and nutrition are cornerstones of health, with likely reciprocal links between the two. The bidirectional link between sleep and food intake has been extensively studied, however, this literature relies almost completely on interventional and epidemiological studies. In the current study, we studied this link under naturalistic conditions, using data from a large sample of healthy participants. We investigated the bidirectional, time-lagged, within-person covariation between sleep, recorded by mobile EEGs and morning questionnaires; and food intake, recorded by retrospective evening questionnaires about the timing, content and satiation of previous-day meals. The findings supported links between sleep and food intake in both temporal directions. Later timing of the last meal was associated with later sleep onset, while a longer fasting period between the last meal and sleep was associated with reduced total sleep time, and reduced sleep efficiency. Sleep efficiency was higher following higher total daily energy intake. Later sleep was associated with a shift of next-day food intake to later hours. Overall, this naturalistic study suggests that the bidirectional relationship between sleep and food intake is primarily related to timing, not quality or composition. Contrary to some recommendations, we found no negative effect of reduced sleep quality after large, late, or satiating last meals.