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BLOG BY Emilia Fish BSc ANutr

How Screen Time Affects Appetite

Appetite is our natural desire to eat food to satisfy our bodily needs. It may result from internal cues such as hunger or external hedonic cues such as foods we find appealing (1, 2). Working from home the past year, I can personally say my screen time has increased. This is consistent with research in 2020 showing an increase in educational screen time and reports of leisure screen time increasing by 265% (3).

In this article, I hope to share the evidence base on how screen time can affect our appetite, but I would like to point out that so can many other factors, and this research is still developing. I think it is important to acknowledge at the start how we can use screen time to relax, learn, connect, and share with others. Moreover, as the first sentence reads, appetite is our natural desire to eat and satisfy our bodily needs. Therefore, it is essential to change the language we use around food, eating, our appetite and snacking – things which are in our nature. Nutrition fuels our body – both physically and by giving us enjoyment, through sharing food and pleasant experiences.

Screen Time vs Sedentary Time

Screen time is the time we spend sat looking at our devices – whether that is a laptop, phone, TV or another source (4). Screen time displaces movement time. In fact, research shows how we almost freeze when looking at screens, like no other daily sedentary activity, such as reading or listening to music. So, a difference between sedentary activities and screen time is a reduction in Non-Exercise Activity Thermogenesis (NEAT) (5). NEAT is the energy expenditure we do not think about – it is the energy we expend to maintain and change posture during everyday activities. On a day-to-day basis, this does not have a significant effect; however, over time, it adds up (6).

Not All Screen Time Is The Same

Not all screen time is of the same quality. For example, today, we are talking about Discretionary Screen Time (DST) – this is leisure screen time, not educational screen time. It has been estimated in the US that on average 8 to 12 -year-olds spend just under 5 hours per day on DTS, while 13 to 18-year-olds spend 7.22 hours per day (7).

Again, there are different qualities within DST. For example, watching something violent on screens triggers an acute stress response compared with non-violent viewing. This can result in cortisol release, the primary stress hormone, which is associated with increased blood sugars, and appetite (8, 9). Further, watching violence on screens has been associated with greater food intake, including a preference for foods high in fat and salt (10, 11).  Furthermore, media multitasking which is “the simultaneous use of and switching between unrelated forms of digital media” such as looking at one thing on our phones while watching something different on TV, has been associated with increased reward responses to appealing foods (12).

Similarly, research finds that our ability to process our satiety cues is dependent on the availability of our attention. Therefore, when watching very engaging DST, we are less likely to perceive that we are full (13). Consistently, research finds that when we are distracted by DST when eating, this affects our ability to form memories that we have eaten. Those are memories which we usually pull on when deciding if we are hungry later on, and if we were distracted, are more likely to then reach for a snack (14, 15, 16). Although, as spoken about initially, no food or snacking is “bad” – food does not have moral values, so we need to be careful about how we interpret this research. What is clear from it is mindful eating – slowing down, acknowledging what and how we are eating – allows us to be present at our meal, enjoy it, and helps us to tune into our hunger and satiety cues both during and after that meal (17, 18).

Screen Time, Sleep, and Appetite

Screen time has also been found to affect our sleep health, with high screen time negatively affecting our ability to fall asleep, exhaustibility, energy levels, and concentration (19). Furthermore, lack of sleep has been shown to downregulate leptin (our “satiety hormone”) and upregulate ghrelin (our “hunger hormone”), overall increasing our hunger and food intake (20).

Mechanisms proposed by which screen time affects our sleep include time placement – particularly with nocturnal screen use (21). Secondly, the media content causes psychological stimulation (21). Thirdly, the blue light emitted from devices may alter our circadian rhythm. This blue light is the same as in daylight, which causes a suppression of melatonin (the sleep-promoting hormone), leading to us being awake for the day. Usually, melatonin increases in the hours before we go to bed; however, its levels can continue to be suppressed by blue light emitted from screens, affecting our sleep (21, 22, 23).  

Research has looked at ways to overcome this, including blue light filtering glasses and putting on our phones on the “night shift mode”. This research is in its infancy and has mixed results (24, 25, 26). On a precautionary principle, as they do no harm, and if they are sustainable for you, blue light filtering screens or glasses, or activating “night shift mode” may be something you choose. Alternatively, reducing screen time and/ or abstaining from screen time in the evening is another option.

Screen Time Recommendation:

1. Considering the mixture of evidence, the World Health Organisation takes a precautionary approach in its recommendations. For 0 to 2-year-olds, no screen time is recommended. For 1-year-olds, DST is not recommended. For 2 to 4-year-olds, DST should be no more than 1 hour per day; less is better (27).

2. Public Health England in 2018 recommended how everyone should be encouraged to reduce the time we spend on screens, including watching TV, playing video games, and using a computer (28).

3. Location of our screens can also make a difference, so it has been recommended they should not be in bedrooms or present during mealtimes. In addition, daily screen-free time should be encouraged (29).

Final words

Remember, we can use screen time for so much good. Our appetite and food gives us so much too - part of the intuitive eating approach talks about “discovering the satisfaction factor”. This is allowing ourselves to enjoy food that we find delicious and satisfying (17, 18). I also like to think about challenging the way we perceive snacking between meals, as it can be used to help keep us fuelled and satisfied throughout the day. Equally, if we can, reducing our screen time, especially during mealtimes and in the evening, can help us focus on our meals and become more attuned to our hunger and satiety cues.

Resources:

• Just Eat It by Laura Thomas. This book guides us through intuitive eating (30).

• Royal College of Paediatrics and Child Health. The health impacts of screen time - a guide for clinicians and parents (31).

• World Health Organisation. Physical activity, sedentary behaviours (including screen time), and sleep recommendations for children under 5-years-old (27).

Bio:

This blog post was written by Emilia Fish, a Food Science and Nutrition graduate and current MSc Clinical and Public Health Nutrition student at UCL. She has interned as part of the Nutrition Rocks team, has experience in research and enjoys sharing evidence-based nutrition, and recipes on @nutritionnourishment. Emilia shares others journeys and experiences in food and nutrition on her podcast, The Nutrition Nourishment Podcast: Sharing Our Journeys.

References:

1. https://www.sciencedirect.com/science/article/pii/S0306453019312971?casa_token=YVPhNrYofy0AAAAA:_SFIIWhm5YAorMqQorSm6PXoZ14bqWy2yV9d0ikzkZeGqBXRGmtRvt8hzpfw8gMFXqiUuCt6tBQ

2. https://www.ernaehrungs-umschau.de/fileadmin/Ernaehrungs-Umschau/pdfs/pdf_2018/07_2018/EU07_2018_Special_Blundell_Englisch.pdf

3. https://www.sciencedirect.com/science/article/pii/S0033062020300967?via%3Dihub

4. https://adc.bmj.com/content/97/11/935.short?casa_token=dpZ_9T2-eoAAAAAA:xWoCY-1fW3ghKRXgu2Wq6QVRgxjfViADLmd_u5-IefJgBNpQfdnrVJZHEaZIsC3JD2iAz9utPchV

5. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0126722

6.https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6058072/#:~:text=NEAT%20is%20the%20energy%20expenditure,other%20activities%20of%20daily%20living

7. https://www.commonsensemedia.org/sites/default/files/uploads/research/2019-census-8-to-18-full-report-updated.pdf

8. https://onlinelibrary.wiley.com/doi/full/10.1002/oby.21790

9. https://www.sciencedirect.com/science/article/pii/B9780128010280002312

10.https://www.sciencedirect.com/science/article/pii/S0195666317300594?via%3Dihub

11. https://www.sciencedirect.com/science/article/pii/S1471015318302538?casa_token=VfAvDYft6ngAAAAA:dNER0u39YhoY_Zy08RimjMwKpIyQfYivOlurS5Y4Z9jcSeLNjwdJpMQSAaBGALbV-HBdsesEom0

12. https://link.springer.com/article/10.1007/s11682-019-00056-0

13. https://pubmed.ncbi.nlm.nih.gov/32795567/

14. https://pubmed.ncbi.nlm.nih.gov/21569808/

15. https://www.sciencedirect.com/science/article/pii/S0195666308005291?casa_token=BNnHeXE8fFMAAAAA:TB_5tVkm2giDAXMhxW-jRVmWIzX774T9eLLJSOj2AciuoWkurCIHzOx8BHRjIW_0aliXYI9frco

16. https://academic.oup.com/ajcn/article/93/2/308/4597636

17. https://www.intuitiveeating.org/

18. https://laura-thomas.com/

19. https://www.mdpi.com/1660-4601/16/3/518

20. https://www.sciencedirect.com/science/article/pii/S1521690X10000722?casa_token=GKFDnetAXV4AAAAA:euaOxV_P312a22RoJIuIUKgeVxNm28N3uGo_Ei3iJWQrmJ3NK3iXYHaLKKyHe0vCymUVN2XjmC8

21. https://journals.physiology.org/doi/full/10.1152/japplphysiol.01413.2009?rss=1

22. https://www.mdpi.com/1660-4601/16/3/518

23. https://pediatrics.aappublications.org/content/140/Supplement_2/S92

24. https://www.tandfonline.com/doi/full/10.1080/07420528.2016.1194289?casa_token=otZ4u5EsS7oAAAAA%3AU8J1UrUXuHOEaIGpPTu3IktqGHOotW9Avt2wqp3Ea0uEkkmg5c0XXYcddSui3nUT12uVvTQVY-j70Q

25. https://www.sciencedirect.com/science/article/pii/S2352721821000607?casa_token=OEPbetIMvqkAAAAA:uxFpPCrV-TwCXSjligHFCSyoRNFRTbxesHcMO69ZDXNMmxr8obk7_dC6ns9VkDXzLMUeFeMme-g

26. https://psycnet.apa.org/record/2020-48711-001?doi=1

27. https://www.who.int/news/item/24-04-2019-to-grow-up-healthy-children-need-to-sit-less-and-play-more

28. https://www.gov.uk/government/publications/health-matters-getting-every-adult-active-every-day/health-matters-getting-every-adult-active-every-day

29. https://pubmed.ncbi.nlm.nih.gov/30354382/

30. http://www.laurathomasphd.co.uk/just-eat-it/

31. https://www.rcpch.ac.uk/resources/health-impacts-screen-time-guide-clinicians-parents

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