Studies have found that sleep is important for the regeneration and repair function of the body. Sleep helps in regulating one’s mood, normalising heart pressure, increasing insulin sensitivity, and increasing immunity and brain functions. The main stages of sleep and their effect on metabolism are as follows:
In NREM sleep, the blood pressure lowers down, body temperature decreases, breathing slows, and the metabolic rate of the body reduces. The body secretes growth hormones (GH) at stage II of NREM sleep. GH lowers blood glucose levels and promotes cell growth.
This is the most metabolically active stage of the sleep cycle. Testosterone and cortisol hormones are released. The brain increases its activity to tone up the muscle, which increases eye movement and leads to dreaming. Our body becomes more insulin sensitive because dreaming requires energy consumption. Therefore, uninterrupted sleep has been linked with increased longevity and decreased obesity.
We burn up to 50 calories per hour during our sleep. This depends on the basal metabolic rate (BMR). BMR is the amount of energy required for performing all the important body functions such as heartbeat, circulation, breathing, temperature control and cell growth and repair. BMR consists of about 80 percent of our total energy requirement, with the brain alone taking 20 percent of daily energy needs.
Sleep is essential for maintaining our circadian rhythm and the daily sleep-wake cycle that acts as our biological clock. It works synchronised to earth’s daily rotation of light and dark and our lifestyle. Circadian rhythm affects various functions of our body such as immune responses, hormonal secretions and levels of neurotransmitters and performs in tune with every cell in the body and brain.
Different hormones play a crucial part in retaining circadian rhythm. Melatonin is a sleep-inducing hormone whose level increases when it is dark. Cortisol is a stress hormone that makes us more alert, whose level decreases at night-time. Another important hormone is leptin, the satiety hormone that prevents hunger when our body does not have sufficient stored fat. At night leptin levels are increased to avoid interruption in sound sleep due to hunger pangs. All this helps in maintaining good metabolic health and unwanted weight gain.
A sedentary lifestyle is one of the most common risk factors for obesity and diabetes, which increases with insomnia and sleep deprivation. Working late nights, shifting duty hours, jet lags, medications and stress are the key causes of an imbalanced circadian rhythm.
Good sleep habits are often identified by scientists as sleep hygiene that helps one to get quality sleep. Some of these are noted below :
It can be concluded that for healthy adults it is essential to have a good seven to nine hours of sleep at night which is even greater for children. Sleeping and a sedentary lifestyle through both low activity processes have different outcomes. Sedentary behaviour leads to obesity whereas; a proper sleep pattern acts as protection against it as well as promotes better metabolic health. Sleep is important for improving mental health, regular body recovery, longer life and all-around wellness.