It is commonly thought that the body and brain shut down for a few hours each night to rest in preparation for the next day. However, neither the body nor the brain shut down when we sleep. They are actually frequently working even harder than they do during the day, undergoing processes to restore cells, process information, and improve health. The body follows a natural 24 hour rhythm of waking hours and sleep called the circadian rhythm. This rhythm is determined by the hours of light and genetics that control hormone release in the body.
Sleep has two main stages: REM and non-REM. The REM phase is a period of vigorous brain activity, which may be responsible for consolidating information and processing memories, which is why babies (whose entire days are full of new experiences the brain needs to process) spend twice as much time in REM sleep than adults do.
The non-REM phase makes up the majority of time spent asleep, during which, the body works to gently lower the heart rate, temperature, and breathing rate.
Among many other functions sleep can promote recovery and cell rejuvenation, produce additional cytokines, which help your immune system fight off infection and facilitate learning and memory.
It is commonly understood that shorter sleep cycles have been linked to an increased risk of obesity. (1)
Studies have suggested that sleep loss might lead to poor food choices favoring the selection of comfort foods with weight-gain potential. Sufficient sleep is suggested as an important mechanistic factor governing appropriate food choices. (2)
Studies have suggested that sleep loss might lead to poor food choices favoring the selection of comfort foods with weight-gain potential. Sufficient sleep is suggested as an important mechanistic factor governing appropriate food choices. (2)
Studies have show that sleeping less than 6 hours or more than 9 hours per night can lead to impaired glucose tolerance, although more research is required to understand the mechanism of action. (3)
Sleep cycles of less than 6 hours or more than 9 hours has shown a trend toward lower HDL levels and higher levels of triglycerides in women and higher incidence of levels of LDL in men. (5)
It is understood that sleep has a strong influence on the metabolic hormones, such as leptin and ghrelin, that regulate energy balance.
It is suggested that bodily inflammation processes are activated by long and short term sleep deprivation and contribute to subsequent sleep complaints and short sleep duration. Elevated CRP levels have been shown in partial and long term sleep deprivation. (4)
The key to good sleep is understanding how much your body needs and making sure that you get enough. In a 22 year study following 21,268 twins, there was a significantly higher mortality rate in those that under slept < 7 hours or overslept >9 hours. (7). While the exact amount varies from person to person, the majority of people do not get enough sleep. The best way to start a healthy sleep routine is to build it into your schedule, and try to be in bed at the same time each night and wake up around the same time each morning.
There are also a variety of tools and trackers on the market that help you to measure your sleep and circadian rhythms, which can be helpful to understand the amount and quality of sleep that you are getting.
(1) https://www.ncbi.nlm.nih.gov/pubmed/18517032
(2) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3763921/#R1
(3) https://www.ncbi.nlm.nih.gov/pubmed/15851636
(4) https://www.ncbi.nlm.nih.gov/pubmed/14975482
(5) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2398756/
(6) https://www.ncbi.nlm.nih.gov/pubmed/8497012
(7) https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2266277/
