Energy expenditure during sleep, sleep deprivation and sleep following sleep deprivation in adult humans.
Level 3 - non-randomized controlled study
Within-subject sequential laboratory interventional study without a randomized control group
PubMed 21059762 · doi:10.1113/jphysiol.2010.197517
What was done
Seven healthy adults (mean age 22 ± 5 years) followed an ~8 h sleep schedule for 1 week and a weight-maintenance diet for 3 days before and during testing. After a habituation night, participants spent 3 days in a whole-room indirect calorimeter. The protocol consisted of 24 h baseline (16 h wake, 8 h sleep), 40 h of continuous sleep deprivation, and 8 h of scheduled recovery sleep. Energy expenditure (EE) was measured continuously across 24 h intervals, daytime, nighttime, and across specific sleep stages.
What was found
Compared to baseline, 24 h total EE increased by ~7% during the first 24 h of sleep deprivation and decreased by ~5% during recovery (which included wake hours 25–40 plus 8 h recovery sleep). Nighttime EE increased by ~32% during the night of sleep deprivation and decreased by ~4% during recovery sleep relative to baseline nighttime EE. EE varied slightly across sleep stages, with brief wakefulness during scheduled sleep episodes associated with increased EE.
Why it matters
Provides direct calorimetric evidence that human sleep serves an energy-conserving function, quantifying the modest metabolic cost of staying awake versus sleeping.
Limits
The sample size is very small (n = 7) and restricted to young, healthy adults. The protocol used a fixed sequential order (baseline, deprivation, recovery) rather than a randomized crossover design, meaning time in the calorimeter or order effects could not be fully controlled. The study evaluated acute total deprivation rather than chronic partial sleep restriction.
Cited by
- supports The difference in energy expenditure between a full night of sleep and staying awake for that duration is only about 140 calories.