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A fixed single meal in the subjective day prevents free-running of the human sleep-wake cycle but not of the circadian pacemaker under temporal isolation
A single meal during the day stops the sleep-wake cycle from drifting but does not reset the internal body clock when isolated from time cues
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Abstract
A fixed single meal at 1800 h did not significantly phase-shift the sleep-wake cycle but influenced circadian rhythms over 8 days.
- When meals were allowed at any time (ad-lib), significant phase delays in sleep-wake cycle and circadian rhythms in melatonin, cortisol, and body temperature occurred.
- In contrast, a fixed meal time at 1800 h did not lead to a significant change in the sleep-wake cycle.
- Most individual subjects showed consistent differential effects from the fixed meal schedule.
- No prefeeding increase in plasma cortisol and leptin levels was observed with the fixed meal schedule.
- Plasma ghrelin levels were high before meals in both ad-lib and fixed meal groups, likely influenced by meal intake patterns.
- A single meal increased plasma insulin levels by four to five times compared to baseline.
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