Our increasingly busy lifestyles are leading to widespread sleep deficiencies. The 2005 Sleep in America poll indicates that, on average within the last 50 years Americans have reported a 1.5-2 hour reduction in sleep per night (Lucassen et al., 2012).
The Benefits of Sleep
The benefits of a good night’s sleep are not just mental. Researchers are finding that good quality sleep is essential to:
- Repair the body’s tissues i.e. muscle, tendons and bone.
- Maintain the cardiovascular system (heart and blood vessels) healthy.
- Regulate and strengthen the immune system.
- Regulate appetite, weight and control blood glucose levels.
Sleep Deprivation, Obesity and Chronic Disease
There is growing evidence that people who get too little sleep (fewer than five to six hours a night) have a higher risk of weight gain and obesity than people who get seven to eight hours of sleep a night (Lucassen et al., 2012).
Data from the 2011-2012 Australian National Health Survey indicate that nearly two-thirds (63 per cent) of the Australian population are now classified as overweight or obese (Australian Bureau of Statistics). These statistics are reflected in important obesity-related complications, such as hypertension, hyperlipidemia, and type 2 diabetes, all leading causes of cardiovascular disease (Lucassen et al., 2012).
The rate of diabetes in Australia has shown a steady increase from 2.4% in 1995 to 3.8% in 2007–08 (Australian Bureau of Statistics). Sleep deprived individuals reportedly have a 35% greater chance of gaining more than 5kg over the course of 6 years (Lucassen et al., 2012).
While obviously a number of factors interplay leading to weight gain, such as exercise and diet, sleep is likely one of the factors. Lack of sleep (less than 6 hours per night) alters our metabolisms in profound ways, increasing the risk of weight gain and chronic disease (Lucassen et al., 2012).
Sleep Deprivation and Weight Control
Sleep is designed by evolution for restoration and repair. When we get a good night’s sleep, our metabolisms are slowed; breathing, digestion, heart rate and movements are decreased so that our energy needs are much lower. In turn, blood sugar levels remain relatively stable throughout the night. If individuals are, on the other hand, kept awake while fasting for about the same time frame, blood sugar levels would fall significantly, which would stimulate the person to eat (Lucassen et al., 2012).
If we look at this through an evolutionary perspective. Our ancestors would have likely remained awake when there was some kind of threat; in this respect, appetite stimulation would have been an advantage resulting in an increased food intake which meant more energy and ability to deal with the threat (Lucassen et al., 2012).
The Appetite Hormones: Leptin and Ghrelin
Poor sleep is linked to the disruption of normal appetite signals. After a night of poor sleep or frequent awakening, the hormone ghrelin is released from the stomach and increases appetite and food intake. In addition, sleep loss is associated with lower levels of the hormone leptin, which is produced in the fat cells and which tells you whether you are full and thus promotes satiety. Sleep loss leads to increased ghrelin and decreased leptin (Berry, Chapter 30, 2011).
Sleep Deprivation and Immune Function
Resent research is linking sleep loss with our immune and inflammatory systems. Research is finding that short sleep promotes a proinflammatory state, which, in turn, exerts its negative consequences on insulin resistance and the immune function, increasing our risks for heart disease and other chronic diseases (Lucassen et al., 2012).
Sleep occurs in cycles, each usually composed of a period of non-rapid eye movement sleep (NREM) followed by a stage of rapid eye movement sleep (REM). There are usually three to five NREM/REM cycles per night. Each stage is important for its own specific homeostatic function. Sleep requirement changes throughout our life reflected by the need for growth and repair as we transition through the stages of young to old. (Berry, Chapter 6, 2011).
A sleep debt is the cumulative effect of not getting enough sleep and long term it takes it’s toll mentally and physically. Sleep Scientist, Dr Chin Moi Chow, from the University of Sydney, lead a study showing that after several nights of getting less sleep than you need, your body builds up a sleep debt that you have to repay by sleeping longer than usual. Dr. Chow’s study found that each person had a different sleep cycle, with some taking only a couple of days to repay the sleep debt, whereas other people take longer (Wong et al., 2013).
Exercise Intensity and Sleep Duration
The body repairs when it sleeps, thus the need for a good quality sleep is essential if your training intensity and duration increases. The quality of your sleep affects your energy levels, recovery, metabolism, muscle growth and muscle, tendon and bone repair. If you train when you are sleep deprived your capacity to repair is decreased and you are more likely to sustain an injury.
Exercise Improves Sleep Quality
Various studies are demonstrating that exercise helps to improve sleep quality. Moderate-intensity aerobic exercise approximately 3 hours before bedtime has been shown to reduce sleep onset latency, total wake time, and pre-sleep anxiety, while increasing total sleep time and sleep efficiency in those diagnosed with insomnia (Passos et al., 2010; Hargens et al., 2013).
Experts universally endorse sleep, exercise, and nutrition as the building blocks for good health. The interrelationship between these three elements is the focus of on going research into this fascinating area.
Berry RB. Fundamentals of Sleep Medicine, Elsevier, 2011.
Hargens TA, Kaleth AS, Edwards ES, Butner KL. Association between sleep disorders, obesity, and exercise: a review. Nat Sci Sleep. 2013 Mar 1;5:27-35.
Lucassen EA, Rother KI, Cizza G. Interacting epidemics? Sleep curtailment, insulin resistance, and obesity. Ann N Y Acad Sci. 2012 Aug;1264(1):110-34.
Passos GS, Poyares D, Santana MG, Garbuio SA, Tufik S, Mello MT. Effect of acute physical exercise on patients with chronic primary insomnia. J Clin Sleep Med. 2010;6:270–275.
Wong SN, Halaki M, Chow CM.The periodicity of sleep duration – an infradian rhythm in spontaneous living. Nat Sci Sleep. 2013 Jan 18;5:1-6.