Abstract
Objectives: Experimental inversion of circadian and behavioural rhythms by 12-hours adversely effects markers of
metabolic health. The objective of this work was to investigate
the effects of a more modest 5-hour delay in behavioural cycles
(as observed in e.g. trans-Atlantic or trans-continental jetlag) on
circadian and metabolic markers.
Methods: Fourteen participants completed an 8-day inpatient laboratory protocol, with controlled sleep-wake opportunities, light-dark cycles, meal timing and diet composition. The
5-hour delay in sleep/wake and mealtimes was induced by
delaying sleep opportunity. We measured melatonin to assess
central circadian phase; markers of postprandial metabolism;
subjective sleepiness, and appetite.
Results: Melatonin rhythms gradually adapted to the new
behavioural cycle. In the 4-hours after the phase delay, there was
slower gastric emptying at breakfast, lower fasting plasma
glucose, higher postprandial plasma glucose and triglycerides,
and lower thermic effect of feeding (p < 0.05). These changes
were abolished or attenuated within 48–72 hours of the phase
delay.
Conclusions: Moderate (5-hour) circadian desynchrony only
transiently disrupts metabolism. Occasional jetlag may therefore
pose low metabolic health risk