Struggling to achieve those goals? Here’s why you should get more ZZZzzz’s

You can exercise all you want, and eat the ‘right’ foods each and every day, but miss out one night of good quality sleep and your metabolism can change so dramatically that it undoes all of the other hard work you have put in.

That’s right. Sleep may well be the missing link in your ability to reach - and maintain - your health and fitness goals.


Research shows just how severely sleep disturbances affects your genes

One of the greatest influences on your ability to build muscle, tone your body, and process the foods you eat lies in the way your genes work. It’s why some people are naturally slim and toned while others have to work very hard at it. Genes, however, aren’t a factor that is fixed. They can be switched on or off according to a variety of factor that come from the environment you live in. This is referred to as epigenetics.

One of these environmental factors that can trigger certain genes to turn on and other to turn off is sleep. There has been a lot of research into the effects of shift work, for example, and its influence on chronic illness. There’s also a significant amount of evidence to support its influence on fitness and weight management.

Let’s start with the latter.


Body composition and weight management is greatly affected by sleep cycle

It is well-known that sleep is a physiological necessity for the body to benefit from its restorative properties. When there are interruptions in sleep, or sleep duration is too long or too short, ill health becomes a risk.

In cases of higher BMI and altered body composition, sleep plays a significant role. In a study published by the Annals of Epidemiology, researchers found during their review of several other studies, that those who sleep less - fewer than 5 hours a night - are in fact more likely to develop obesity than those who sleep for longer durations. In addition, the risk factors for obesity increase over time where sleep duration becomes shorter and shorter1,2.

It’s interesting what happens in the body as a result. Because the time needed for the body to repair and restore itself is cut short, inflammation increases. Inflammation is associated with various physiological chemical pathways being activated, one of the is the stress pathway. This form of stress tells the body to increase its production of two critical stress hormones called adrenaline and cortisol, where cortisol is an energy sparing hormone, which has a direct influence on body composition. Prolonged release of cortisol increases body fat percentage, and in doing so, makes it harder for you to lose weight and maintain muscle mass and tone3.

There’s another element at play here, too. When there is a consistent rise in your cortisol levels, it also influences your appetite. You’re more likely to choose higher calorie-dense food and your cravings for refined, energy-rich carbohydrates goes up. A tired body and mind often has less willpower to say no, and so a vicious cycle of sleep deprivation, fatigue, inflammation, stress and cravings begins4,5.

What about physical effects of sleep deprivation and your ability to take part in a regular exercise routine?


Total energy expenditure decreases during periods of sleep deprivation

It seems obvious that too little sleep means you’re going to be more fatigued and less likely to want to be active6, yet it’s common for individuals to continue to function in sleep deprived states and make many other attempts to improve their health and wellbeing other than to fix their sleep7.

Multiple studies have shown how in athletes, particularly prior to competition, sleep loss is a common occurrence even though it affects their athletic performance. While there is conflicting evidence that suggests that in some cases performance can be compromised due to sleep deprivation, and in other cases performance may be maintained, there is consensus that chronic sleep loss can bring about symptoms of overtraining syndrome8,9,10. Now, of course this is in trained, professional athletes. What about those of us who take part in physical activity as a means to boost our health and wellbeing in a recreational setting?

Studies show that it’s best to get enough sleep if you want to maintain these positive habits and benefit from them like you want to11.

In our fast-paced, always-on world, we tend to forget about the essentials of sleep. Sleep, and good quality sleep at that, is simply a non-negotiable when it comes to your overall health. If you’re not sleeping enough, or you’re sleeping too much, your body is not functioning as it should and it can cause many of its intricate processes to go haywire. Sleep also gives you an opportunity to recover mentally and emotionally, which makes it easier for you to stay motivated to continue to work on your health and fitness goals, and may allow you to enjoy them more fully when you achieve them. As someone dedicated to their health and fitness, make sleep a part of your everyday routine. Give it as much attention you do your diet and activity levels and you may be surprised at the array of benefits you reap in return.



  1. Wirth, M., et al. Association between actigraphic sleep metrics and body composition. Annals of Epidemiology. 2015. 25(10), 773–778.
  2. Wu, Y., et al. Sleep duration and obesity among adults: a meta‐analysis of prospective studies. Sleep Med. 2014. 15:1456– 1462.
  3. St-Onge, M. Sleep–obesity relation: underlying mechanisms and consequences for treatment. Obesity Reviews. 2017. 18(S1).
  4. Rossum, E. Obesity and Cortisol: New Perspectives on an Old Theme. Obesity. 2017. 25(3):500-501.
  5. Bessey, A., et al. 0236 Changes in State Anxiety over 62 hours of Sleep Deprivation and Subsequent Recovery. Sleep. 2018. 41(S1):A91–A92.
  6. Parrish, J., & Teske, J. Acute partial sleep deprivation due to environmental noise increases weight gain by reducing energy expenditure in rodents. Obesity. 2017. 25(1):141-146.
  7. Penev, P. Update on Energy Homeostasis and Insufficient Sleep. J Clin Endocrinol Metab. 2012. 97(6): 1792–1801.
  8. Davenne, D. Sleep of athletes—problems and possible solutions. Biol Rhythm Res. 2009. 40(1):45–52.
  9. Samuels, C. Sleep, recovery, and performance: The new frontier in high-performance athletics. Neurol Clin. 2008. 26(1):169–80.

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