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The importance of sleep for a healthy lifestyle

18 April 2019

By Caroline Holland- Dietitian and Health Coach

Sleep is one of our basic human needs however it is a complex and vast topic. In part 1 of this blog we will focus on understanding sleep and start to explore how poor sleep affects health. In part 2, we will look at some top tips to help improve sleep quality.

Understanding sleep:

Sleep is a fundamental need for the body. It affects emotional well-being, cognitive function, daytime performance and physical health. Poor sleep quality can influence weight and appetite and has been associated with obesity, diabetes, hypertension and cardiovascular disease risk in many studies.1

Circadian rhythm is a biological 24 hour clock. It influences sleep-wake cycles, hormone release, eating habits, digestion, body temperature and other bodily functions.2

Circadian rhythm is controlled by the brain and external factors such as light and temperature. When it becomes dark, this signals the brain to produce a sleep hormone, melatonin.

Stages and duration of sleep:

We cycle through two basic stages of sleep several times during the night: non-rapid eye movement (NREM) sleep which consists of 4 stages and rapid eye movement (REM) sleep.3

Within the 4 stages of NREM we see a changeover from wakefulness to sleep. Heartrate, body temperature, breathing and eye movements slow and muscles become relaxed. Stage 4 of NREM sleep is the most restorative sleep leaving us feeling refreshed in the morning.

REM sleep occurs roughly 90 minutes after falling asleep. In this stage heartrate and breathing increases, eye movements are rapid and the majority of dreams, learning and memory happen in this stage (it is thought both stages are important for memory).

The recommended duration of sleep varies across the lifespan. For most adults, 7-9 hours is thought to be optimal whereas a child can require between 8-15 hours of sleep per day.4

What causes poor sleep?

Several lifestyle factors can contribute to poor sleep quality as they disrupt circadian rhythms.

The top culprits include caffeine and alcohol consumption, diet, electronic media exposure, bright lights during night hours, stress, shift work and timing of sleep.

How does poor sleep affect our health?


A lack of sleep can weaken the immune system and increase susceptibility to infection such as the common cold.5 One study highlighted how inadequate sleep can trigger an immune system response in the body, increasing inflammation and causing tissue damage. This helps us to further understand the link between sleep problems and increased risks for diseases like diabetes, arthritis, heart disease, obesity and specific cancers.6

Heart health

It is not fully understood why poor sleep is detrimental to heart health. It is thought to be linked with underlying health conditions and biological processes like glucose metabolism, blood pressure, and inflammation. Getting less than 7 hours of sleep has been linked with increased risk and incidence of cardiovascular disease and poor cardiovascular health outcomes, including hypertension, hypercholesterolemia, myocardial infarction and cerebrovascular accident.7


Poor sleep has been associated with reduced post prandial insulin secretion and increased secretion of the stress hormone cortisol. Cortisol can worsen sleep and reduce the effectiveness of insulin leading to raised blood glucose levels and increased risk of developing Type 2 Diabetes.

Experimentally induced sleep loss in healthy volunteers decreased insulin sensitivity without adequate compensation in beta-cell function, resulting in impaired glucose tolerance and increased diabetes risk.8


There is a complex relationship between inadequate sleep and obesity. Lack of sleep can affect appetite controlling hormones and pleasure systems in the brain leading to poor food choices, overeating and weight gain. Additionally, fatigue reduces the engagement in physical activity which can drive further weight gain.

Although further research is required, some studies associated poor sleep with down-regulation of the satiety hormone leptin and up-regulation of the appetite-stimulating hormone ghrelin, leading to increased hunger and food intake.8

One small study looked at the association between sleep restriction and activation of the endocannabinoid (eCB) system which is a key component of hedonic pathways involved in modulating appetite and food intake. Participants who were sleep deprived had increased appetite and hunger and were more likely to choose high fat, high calorie, palatable snacks even after consuming a nutritious meal 2 hours prior to being offered these snacks.9

Mental well-being

Poor sleep and mental well-being have a converse relationship. Worry, stress and anxiety disrupts sleep whereas, poor sleep can lead to anxiety disorders and exacerbate stress. It’s a vicious cycle.

Seasonal affective disorder (SAD) can cause oversleeping or irregular sleeping patterns. This can increase risk of isolation, loneliness and depression if missing out on socialisation.

Post-traumatic stress disorder (PTSD) can cause nightmares and night terrors which disturbs sleep.10

We have touched upon the consequences of poor sleep on health. If the complexities of sleep have not already caused you to drift off to sleep, stay tuned for part 2 to learn some tips for improving sleep quality.

Caroline is a Registered Dietitian with a degree in BSc(Hons) Nutrition and Dietetics and further qualifications in NLP and masters level Behaviour Change Skills. She is currently participating in a Mindfulness course. She has practiced as a Dietitian in both the community and acute services within the NHS and more recently in the private sector as a Roche Diabetes Care Health Coach on the OurPath programme. Caroline is passionate about using her skills in both the prevention of long term health conditions and to improve the health and quality of life of individuals. She enjoys spending time with family and friends, travelling, keeping fit through dancing and running and loves the great outdoors and baking.

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  1. Golem, D., Martin-Biggers, J., Koenings, M., Davis, K. and Byrd-Bredbenner, C. (2014). An Integrative Review of Sleep for Nutrition Professionals. Advances in Nutrition, 5(6), pp.742-759.
  2. (2019). Circadian Rhythms. [online] Available at: [Accessed 2 Feb. 2019].
  3. Psychology Today. (2019). Your Sleep Cycle Revealed. [online] Available at: [Accessed 4 Feb. 2019].
  4. The Sleep Council. (2019). How much sleep do we need? - The Sleep Council. [online] Available at: [Accessed 14 Jan. 2019].
  5. Ibarra-Coronado, E., Pantaleón-Martínez, A., Velazquéz-Moctezuma, J., Prospéro-García, O., Méndez-Díaz, M., Pérez-Tapia, M., Pavón, L. and Morales-Montor, J. (2015). The Bidirectional Relationship between Sleep and Immunity against Infections. Journal of Immunology Research, 2015, pp.1-14.
  6. Mullington, J., Simpson, N., Meier-Ewert, H. and Haack, M. (2010). Sleep loss and inflammation. Best Practice & Research Clinical Endocrinology & Metabolism, 24(5), pp.775-784.
  7. Altman, N., Izci-Balserak, B., Schopfer, E., Jackson, N., Rattanaumpawan, P., Gehrman, P., Patel, N. and Grandner, M. (2012). Sleep duration versus sleep insufficiency as predictors of cardiometabolic health outcomes. Sleep Medicine, 13(10), pp.1261-1270.
  8. Knutson, K. and Van Cauter, E. (2008). Associations between Sleep Loss and Increased Risk of Obesity and Diabetes. Annals of the New York Academy of Sciences, 1129(1), pp.287-304.
  9. Hanlon, E., Tasali, E., Leproult, R., Stuhr, K., Doncheck, E., de Wit, H., Hillard, C. and Van Cauter, E. (2019). Sleep Restriction Enhances the Daily Rhythm of Circulating Levels of Endocannabinoid 2-Arachidonoylglycerol.
  10. (2019). Sleep problems | Mind, the mental health charity - help for mental health problems. [online] Available at: [Accessed 14 Jan. 2019].

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