4. Discussion
Late-night sleep loss, appetite, sleep loss, neuroendocrine appetite, Social jetlag
JETLAG
In this balanced crossover experiment, we examined the effects of the timing of sleep loss on the regulation of hunger and appetite in humans. ‘Late-night sleep loss’, but not ‘early-night sleep loss’, elevated ghrelin concentrations, as well as feelings of hunger and appetite, and desire for food during the subsequent morning was observed, whereas leptin concentrations were not affected by acute sleep loss per se nor timing of sleep loss. Our data show a more pronounced effect of acute sleep loss on ghrelin, hunger, appetite, and the desire to eat when sleep is restricted in the second half of the night compared to a restriction of sleep during the first half of the night. This underscores the chronobiological role of timed sleep loss in human appetite regulation.Studies on the effects of sleep restriction (with different timing) on plasma ghrelin and leptin levels have yielded inconsistent results. Our group showed increased ghrelin levels after one night of partial sleep restriction (sleep from 22:30 to 03:30 h) compared to a night with 7 h of sleep [We showed elevated feelings of hunger and appetite, as well as desire for food, when sleep was restricted, again, in the late part of the night. McNeil et al. evaluated the effects of shortened sleep (~4 h) using an advanced wake time (similar to our ‘late sleep loss’ condition) vs. a delayed bedtime condition (similar to our ‘early sleep loss’ condition) in 18 healthy young men and women [Interestingly, a 3.5 h sleep condition using an early night sleep loss protocol (wake until 03:30 h) for three days in healthy men increased hunger and prospective food consumption, as reported by Hibi and co-workers [Other have also shown increased explicit wanting and liking for high-fat relative to low-fat foods after short sleep with advanced wake time vs. a control sleep condition [Chronic circadian disruption not on only occurs during insufficient and short sleep, but also during rotating shift work or (social) jetlag and, thus, affects neuroendocrine appetite regulation. Social jetlag is a common form of circadian rhythm disruption and presents in up to 70% of the population [Under an acute sleep restriction setting, experimental studies report on increased caloric intake due to night-time calories. On the other hand, it has been shown, both in mice and humans, that feeding either at normal eating time while performing a rotating shift work paradigm [We assessed appetite regulation and desire for food after only one night of sleep restriction by four hours compared to control sleep of 8 h. Therefore, we cannot draw any conclusions concerning the effects of longer-lasting sleep restriction or, on the other hand, shifted sleep, as well as social jetlag. Further studies are needed to evaluate the prolonged effects of sleep restriction with altered sleep timing, e.g., using a forced desynchrony protocol [