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(OR17-04-26) Could We Hibernate for Deep Space Missions? Appetite and Metabolic Responses to Cold-Induced Hypometabolism

Monday, July 27, 2026
11:06 AM - 11:18 AM ET
Location: Maryland Ballroom C
Disclosure(s):
Emily Nigro, B.S. Dietetics: No relevant financial relationship(s) with ineligible companies to disclose.
Objectives: Long-duration space missions require innovative strategies to reduce payload and improve crew health. Hibernating animals can undergo long periods of hypometabolic states while maintaining musculoskeletal mass. The main objective was to determine the impact of repeated cold-induced hypometabolic state on appetite and energy homeostasis in healthy adult participants.

Methods: In a 5-day observational study, 5 healthy adults were individually subjected to 20h/day of cold-induced hypometabolism (Cold-Sleep). Over the next 4 waking hours, participants ate and engaged in exercise. Constant glucose monitors were used throughout the study, and visual appetite scales (VAS) were given before and after each meal. Blood samples were used to assess hormones and metabolic markers; and indirect calorimetry was performed.

Results: Cold-Sleep reduced resting energy expenditure by ~20%; but glycemia remained stable at 115+/-4 mg/dL throughout. Indirect calorimetry showed a steady increase in respiratory quotient from 0.78 to 0.86; and in blood urea nitrogen levels. No significant correlation between hunger and satiety was found immediately upon awakening; while VAS completed after the meal showed an expected negative correlation (i.e., participants with highest satiety scores had lowest hunger scores, p=0.008). Several hormones were impacted by repeated Cold-Sleep. Specifically, ghrelin levels showed a 47.2% reduction from baseline to endpoint. Levels of 3-methylhistidine increased by 95% over the same period (p=0.02).

Conclusions: Glucose homeostasis was maintained during Cold-Sleep, however appetite seems to be more impacted, as evidenced by the lack of reciprocity between hunger and satiety scores upon awakening. Consuming a meal was sufficient to re-establish normal association. Repeated bouts of Cold-Sleep greatly impacted hormone levels and showed that proteins were being increasingly utilized to provide energy. This study demonstrates the impact of Cold-Sleep on energy and metabolic homeostasis and may help us better understand the mechanisms involved during hypometabolic states.

Funding Sources: This work was funded by TRISH and the NASA RI Space Grant Consortium.