This piece was written by one of our contributors; medical student – Mary Moore
Today’s modern world has seen a dramatic increase in people reporting inadequate sleep quality and time spent sleeping. This has coincided with changes in our current lifestyles, recent evolutions in technology, and 24h workplaces. Inadequate sleep is an emerging risk factor for many health issues. Healthcare professionals and researchers have become interested in treatments that may ‘counteract’ the harmful effects of poor sleep or a lack of sleep.
In this blog post we will address how a lack of sleep can impact metabolic health. The article will then touch on how exercise may or may not be beneficial in combating the effects of sleep loss and its negative effects on our metabolic health. At the end of some sections I will include a ‘takeaway point’ to highlight important information.
Several studies have shown that periods of sleep restriction or reduced time in bed (4 to 5 hours sleep per night), can cause a significant reduction in a range of factors related to normal metabolic health, and skeletal muscle health. The current recommendations for adequate sleep are 7 to 9 hours per night for adults (1). However, many of us do not currently meet these recommendations as a result of our lifestyle or occupation. We now know inadequate sleep is a risk factor for metabolic diseases (such as obesity and diabetes) and there is huge interest in understanding how lack of sleep impacts our health and whether treatments such as exercise can be used to counteract this (1,2,3).
Effect of inadequate sleep on metabolic health
In young healthy adults, Inadequate sleep over a period of five to seven nights (4 hours sleep per night) impaired the ability of the body to handle sugar, compared with a normal sleep routine (7 to 9 hours per night) (2, 3). These changes were also linked to unfavourable changes in genes controlling a normal circadian rhythm (our body’s internal clock) and skeletal muscle health (2, 3). Unbeneficial changes such as these have been linked to the development of obesity and type 2 diabetes, in the long term.
A recent short-term (5 days) study examined the effect of exercise training during a period of sleep restriction as a means to ‘counteract’ the harmful effects of inadequate sleep on metabolic health (2). The researchers showed that three sessions of high intensity interval exercise during a one-week period of sleep restriction (4 hours sleep per night for 5 nights) was effective in preventing the negative effects of sleep restriction on the body’s metabolism.
Takeaway point: This suggests that cardiovascular exercise may help to protect against the effects of short-term sleep restriction on metabolic health, but we do not know if it works for long term sleep restriction, like many of us experience during a typical work week.
What about modest sleep loss?
With sedentary lifestyles and reduced sleep hours becoming increasingly common, some studies have explored the effects of sleep loss during a ‘typical work week’ on metabolic health. This is important information given that the majority of the general population experience a modest sleep restriction (~5-6 hours per night) rather than the more severe sleep restriction (~4 hours per night) discussed in this blog post so far. These studies have shown that 5 nights of 5-6 hours of sleep also harmed the body’s metabolic health (4, 5). Interestingly, one study showed performing aerobic exercise each day over a 5-day period was not effective in preventing the negative effects of sleep restriction (6 hours sleep per night for 5 nights) on the body’s metabolism (4). Interestingly, in the same study the researchers showed that two nights of recovery sleep over the weekend (8+ hours per night) restored the metabolic health of the body to normal levels, regardless of whether the individuals were exercising or not.
Takeaway point: This study highlights the importance of getting adequate sleep (or recovery sleep) to restore metabolic health and that exercise may not always be effective in preventing the negative effects of sleep loss (4).
It is important to note that the studies discussed until now took place over a one-week period and so do not reflect the effects of repeated sleep loss that we may experience each week during a typical ‘work week’. One study recently showed that the improvements we see in metabolic health after catching up on sleep over the weekend is lost when we go back to only getting 4-6 hours sleep each night on the weekdays (5).
Takeaway point: This highlights the importance of getting adequate sleep each night for our overall health from week to week.
Take home points on sleep and exercise
- It is clear that the effects of exercise on sleep restriction are very mixed and much more research is required to tease out the relationship between the two.
- While exercise appears to help prevent some of the unfavourable metabolic changes seen with sleep loss it does not completely make up for losing out on sleep.
- You should try your best to adhere to the current recommendations for adequate sleep, which are 7 to 9 hours per night for adults. Check out previous blog posts on sleep and sleep hygiene on The Food Medic Educational Hub.
- You should exercise as part of a healthy balanced lifestyle. According to the NHS the current physical activity guidelines are 30 mins of moderate intensity exercise most days of the week or 20 minutes of vigorous intensity exercise 2-3 times per week (7). Consult your doctor before starting an exercise program.
(1) UK Sleep Council https://sleepcouncil.org.uk/
(2) Saner, N. J., Lee, M. J. C., Pitchford, N. W., Kuang, J., Roach, G. D., Garnham, A., … & Bartlett, J. D. (2020). The effect of sleep restriction, with or without high‐intensity interval exercise, on myofibrillar protein synthesis in healthy young men. The Journal of physiology, 598(8), 1523-1536.
(3) Saner, N. J., Bishop, D. J., & Bartlett, J. D. (2018). Is exercise a viable therapeutic intervention to mitigate mitochondrial dysfunction and insulin resistance induced by sleep loss?. Sleep Medicine Reviews, 37, 60-68.
(4) Jay W. Porter. 2020 SLEEP, EXERCISE, AND INSULIN SENSITIVITY, Dissertation. Unpublished.
(5) Depner, C. M., Melanson, E. L., Eckel, R. H., Snell-Bergeon, J. K., Perreault, L., Bergman, B. C., … & Wright Jr, K. P. (2019). Ad libitum weekend recovery sleep fails to prevent metabolic dysregulation during a repeating pattern of insufficient sleep and weekend recovery sleep. Current Biology, 29(6), 957-967.
(6) Nedeltcheva, A. V., Kessler, L., Imperial, J., & Penev, P. D. (2009). Exposure to recurrent sleep restriction in the setting of high caloric intake and physical inactivity results in increased insulin resistance and reduced glucose tolerance. The Journal of Clinical Endocrinology & Metabolism, 94(9), 3242-3250.