In the first-ever quantification of energy expended by humans during sleep, a University of Colorado team has found that the metabolic cost of an adult missing one night of sleep is the equivalent of walking slightly less than two miles.
The new findings will help researchers further understand one of the important functions of sleep in humans, said CU-Boulder Associate Professor Kenneth Wright. Wright, who led the study, said the goal was to measure and quantify energy expenditure during both sleep and wakeful periods.
"We found that people do expend more energy when they are awake in bed than when they are asleep," he said. The findings showed the eight hours of sleep saved roughly 135 calories over eight hours of wakefulness.
"While the amount of energy savings for humans during sleep may seem relatively small, it actually was a little more than we expected," said Wright, a faculty member in CU-Boulder's integrative physiology department and director of CU-Boulder's Sleep and Chronobiology Laboratory.
A paper on the subject was published in the January issue of the Journal of Physiology. Co-authors included CU-Boulder's Christopher Jung and Emily Frydenall, as well as Assistant Professor Edward Melanson, Dr. Leigh Perreault and Dr. Robert Eckel of the University of Colorado School of Medicine. Jung, first author on the paper, got his doctorate from CU-Boulder in 2009 and is now at the University of Alaska.
The study showed that compared to a typical night of sleep, the amount of energy expended by study subjects during 24 hours of sleep deprivation was up about 7 percent. In contrast, energy expenditure decreased by about 5 percent during the recovery episode, which included 16 hours of wakefulness following the sleep deprivation night, then eight hours of recovery sleep, Wright said.
"Understanding the function of sleep, especially in humans, is considered one of the most important scientific
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University of Colorado at Boulder