Schmid S.M. et al.
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(Journal of Sleep Research, 2008): reducing sleep to 4 hours for two consecutive nights causes a 22% increase in circulating ghrelin compared to 7 hours of normal sleep, with leptin reduction and increased self-reported hunger.
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The speed of the effect: 48 hours are enough
Two nights of reduced sleep produce a measurable, statistically significant hormonal effect.
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Those who chronically sleep 5–6 hours — common among executives — experience a systemic, continuous hormonal alteration.
The mechanism: brain interprets short sleep as energy shortage
Evolutionarily, reduced sleep was associated with danger.
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The brain responds by activating hunger as an energy compensation mechanism. Ghrelin increases to drive food-seeking — a biological trap in the modern food environment.
Leptin and ghrelin: the dual appetite control system
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Sleep deprivation alters both simultaneously: ghrelin rises, leptin falls. A double blow to food control that no willpower can counterbalance indefinitely.
How the Digital Twin uses this information
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The Digital Twin calculates a 'Hunger Risk Index' every morning based on the previous night's sleep. If the profile indicates high probability of elevated ghrelin, the system notifies: 'Attention: last night's sleep may increase hunger today.'
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Schmid S.M. et al. — Journal of Sleep Research (2008) — https://pubmed.ncbi.nlm.nih.gov/18564298/ · pubmed.ncbi.nlm.nih.gov
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