Decremental reset in basal metabolism during 20-days bed rest.

Changes in basal metabolism during 20 days bed rest were measured in 9 young healthy males and 5 females. Food intake was unrestricted and supplementary meals were allowed. All food intake was monitored. A special sleeping pattern was not enforced, although an ordinary day-night diurnal rhythm was kept in the rooms. Body temperatures were measured daily every 2 hours from 7:00 to 22:00. Basal oxygen uptake decreased significantly during the first 10 days of bed rest and levelled off during the following 10 days. Body weight and composition remained substantially unchanged in spite of a decreased energy consumption during the bed rest. In conclusion, basal VO2 was reset at a decreased level during the first 10 days of bedrest with no relationship to the dietary energy intake or to the body temperature, while no more change took place during the following 10 days.