Why is sleep so important?
Sleep is important for many metabolic processed within the body.
Sleep requirements differ depending on age. Adults and adolescence should aim to have 8 and 10 hours of sleep per night, respectively.
Loosing just 2 hours of sleep can result in:
Reduced alertness and concentration
Slower reaction time, poorer judgement
Reduced decision-making skills
Poorer memory
Increased errors
Loss of motivation
Impacts negatively on performance (i.e. increased injury & slower healing)
But did you know that lack of sleep and diet is linked?
What is the link?
Lack of sleep has the ability to alter physiological processes within the body and disrupt the endocrine system by altering hormone secretion, which can effect weight, appetite, stress and increase risk of developing chronic diseases (obesity and type 2 diabetes).
But it’s not all bad news!!
The evidence also suggest that the hormone imbalances involved in weight, appetite and stress, may be able to be reversed by catching up on sleep or during sleep recovery.
(Disclaimer: if you have a chronic condition, sleep will not reverse your condition. However, it may help with treatment effectiveness, such as tackling those cravings and helping with weight loss. Sleep should also be paired with healthy eating and exercise! Seek help from you GP or dietitian for more info)
Heres what the science says:
1. Lack of sleep can increase appetite.
How do you ask? By altering the hormone that regulate your appetite.
Ghrelin is your hunger hormone
Leptinis your fullness/satiety hormone
Sleep deprivation has been found to alter these hormones.
One study compared levels of these hormones in 2 sleeping groups. They found that when people slept less then 4 hours per night for 6 nights, they had increased feelings of hunger. When they looked at their hormone levels they found that in this group there was a 24% increase in ghrelin and 18% decrease in leptin, when compared to the people who got 8 hours of sleep.
These changes in hormones were also seen even in people that got less than 8 hours of sleep. The less sleep you get, the more you ghrelin you secrete.
Studies have also found that sleep deprivation can also impact your food choices. When people are sleep deprived they tend to having higher cravings for and eat excessive amounts of energy-dense, high carbohydrate foods which contributes to overeating and weight gain.
Therefore, acute or chronic sleep deprivation may alter normal appetite regulation and increase the risk of weight gain. Also increasing the risk of insulin resistance, glucose intolerance an increased risk of diabetes.
2. Lack of sleep can increase stress within the body
The bodies stress hormone is Cortisol . Usually, there is a rapid decline in cortisol levels in the evening. However, in sleep deprived people , cortisol levels decline much slower. One study suggests that the elevated levels of cortisol as a result of sleep loss may lead to the development of insulin resistance.
3. Lack of sleep reduced recovery and may lead to weight gain
Normally Growth Hormone (GH) levels increase during sleep and peak shortly after the falling asleep. However, when you don't get enough sleep, growth hormone levels are lower GH . Low GH levels in adults can slow down recovery, slow down the metabolis, lead to unwanted weight gain, elevated triglycerides and insulin resistance which also increases the risks of obesity and type 2 diabetes. This shift in nocturnal GH secretion causes there to be increase GH secreted during the day and during sleep recovery. Therefore, with sleep GH secretion can return to normal.
4. Sleep deprivation may increase risk of Insulin resistance
Sleep plays a role in the control of blood glucose levels and sleep deprivation has been shown to have adverse effects on carbohydrate metabolism and endocrine function, as we have discussed above.
Evidence suggests that even short-term sleep loss significantly impairs glucose metabolism and reduces insulin sensitivity in healthy. A study found that restricting sleep to 4 hours per night over a period of 5 days decreased insulin sensitivity by 25%, which may have resulted from increased lipolysis and fatty acid levels as a result of elevated cortisol levels and/or reduced GH. As we can see they all relate to each other in some way.
Another study also concluded impaired glucose tolerance can occur when sleep was restricted to 4 hours per night for a total of 6 days subjects. In this study glucose disappearance was 40% slower in sleep deprives patients and acute insulin response to glucose was reduced by 30%.
What does this mean?
Lack of sleep also changes many other physiological and complex processes in our bodies.
In summary, Lack of sleep has the ability to affect our hormones and affect our food choices.
Lack of sleep can cause us to feel hungrier and reach for those sugar/sweet foods! Which ultimately cause us to eat in a calorie surplus, causing us to gain weight.
Lack of sleep also affects our energy levels and we are less motivated and less likely to exercise because we are tired.
Just like healthy eating and exercise, good quality sleep should also be a priority!
It is not all bad news! One night of poor sleep is not going to do you any harm! Even lack of sleep for a few nights is not going to cause you and lasting damage. There is some evidence out there that you can repay your sleep dept!
Furthermore, when the effects of sleep deprivation may be reversed, and hormone secretion can return to normal when the sleep debt is repaid. However, the effects of severe sleep and ongoing sleep deprivation is unknown.
Common causes of inadequate sleep
How can I improve my sleep?
There are many ways to improve sleep.
Eating a healthy diet but avoid stimulants like caffeine and alcohol an hour before bed and give yourself time to digest your evening meal before bed time
Exercise regularly t boost your energy levels throughout the day and prepare your body to wind down by chosing quieter activities at night
Having a night time routine. Go to bed at the same time every day
Putting your phone and laptop away and not using them right before bed. The blue light can effect you body clock
Make sure your bed is comfortable.
Keep your room dark and quiet
Sweet dreams xx
Want to read more, nerd out on these!!
Calvin, AD, Carter, RE, Adachi, T, Macedo, PG, Albuquerque, FN, Walt, C, Bukartyk, J, Davison, DE, Levine, JA & Somers, VK 2013, ‘Effects of experimental sleep restriction on caloric intake and activity energy expenditure’, Chest, vol. 144, no. 1, pp. 79-86.
Cauter, E, Spiegel, K, Tasali, E & Leproult, R 2008, ‘Metabolic consequences of sleep and sleep loss’, Sleep Medicine, vol. 9, no. 1, pp. 23-28.
Kim, TW, Jeong, J & Hong, S 2015, ‘The impact of sleep and circadian disturbance on hormones and metabolism’, International Journal of Endocrinology, vol. 2015, no. 1, pp. 1-10.
Leproult, R & Cauter 2010, ‘Role of Sleep and Sleep Loss in Hormonal Release and Metabolism’, Endocrine Development, vol. 17, no. 1, pp. 11-21.
Lucassen, EA, Zaho, X, Rother, KI, Mattingly, MS, Courville, AB, Jonge, L, Csako, G & Cizza, G 2013, ‘Evening chronotype is associated with changes in eating behaviour, more sleep apnea, and increased stress hormones in short sleeping obese individuals’, PLoS One, vol. 8, no. 3, pp. e56519.
Magee, CA, Huang, X, Iverson, DC & Caputi, P 2009, ‘Acute sleep restriction alters neuroendocrine hormones and appetite in healthy male adults’, Sleep and Biological Rhythms, vol. 7, no. 1, pp. 125-127.
Reynolds, AC, Dorrian, J, Liu, PY, Van Dongen, HP, Wittert, GA, Harmer, LJ & Banks, S 2012, ‘Impact of five nights of sleep restriction on glucose metabolism, leptin and testosterone in young adult men’, PLoS One, vol. 7, no. 7, pp. 41218.
Spiegel, K, Tasali, E, Penev, P & Cauter, E 2004, ‘Brief communication: sleep curtailment in healthy young men is associated with decreased leptin levels, elevated ghrelin levels, and increased hunger and appetite’, Annals of Internal Medicine, vol. 141, no. 11, pp. 846-850.
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