Do junk food make us sleep worse?
Sufficient sleep and good sleep quality are essential for a healthy life. During sleep, the body recovers from the stresses of the day. Cell damage is repaired and cells are renewed, the immune system is activated, detoxification reactions take place and metabolic processes and the endocrine system are regulated.
Furthermore, the brain processes the events of the day and forms new memory structures. Disturbing our sleep has a variety of negative effects on our health.
Scientists from the University of Uppsala in Sweden investigated how an unhealthy diet affects our sleep parameters, i.e. the duration and quality of the individual sleep phases. They published their research results in May 2023 in the journal Obesity ( 1 ).
course of the study
15 healthy young men who were of normal weight and had normal sleeping habits with 7 to 9 hours of night sleep were selected as study participants.
The study was set up as a so-called crossover study, so that each subject went through both study phases in random order. Each phase had a different diet plan that the participants followed for one week at a time. Meals were provided by the researchers. One diet plan was healthier and the other followed a “typical Western diet” with higher levels of sugar and saturated fat and lower levels of plant fiber (dietary fiber).
The amount of calories in both diets was the same and was calculated according to the personal needs of the participants. Alcohol and caffeine were avoided during the study period. There was a break of about 7 weeks between the two study phases. At the end of each study phase, the subjects were examined in a sleep laboratory for several days.
What sleep phases are there?
Human sleep consists of different sleep phases that are repeated in cycles several times a night and last around 90 to 110 minutes in total. Each of these sleep phases is characterized by a specific electrical brain activity, the frequency of which can be measured as so-called brain waves in an electroencephalogram (EEG) (2).
A distinction is made between so-called REM sleep (Rapid Eye Movement) and non-REM sleep. REM sleep is characterized by rapid movements of the eyeballs and increased brain activity. In this sleep phase, one often dreams very intensely and experiences are processed and memories are formed ( 3 ).
Non-REM sleep is divided into 3 sleep phases: falling asleep, light sleep and deep sleep. The frequency of the brain waves continues to decrease until deep sleep. Delta waves are the characteristic brain waves that occur during deep sleep. In this phase, the body recovers, the immune system is strengthened and tissue regeneration takes place (4).
Read here what you can do for a healthy sleep:
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Impairment of deep sleep due to unhealthy eating
After just one week on the high-sugar, high-fat, low-fiber “Western diet,” various parameters of the study participants’ deep sleep phases were impaired. There were fewer delta waves overall than with undisturbed deep sleep. In addition, the delta waves also showed a lower intensity than usual.
These results indicate a decreased ability of the body to regenerate after consuming junk food. The effects were evident even the night after the participants returned to a healthier diet.
The total sleep duration and the length of the individual sleep phases showed no change. According to the researchers, this could also be due to the rather short duration of the study.
Conclusion: Junk food disturbs sleep and makes you sick
Even after the short period of one week, unhealthy food affects our sleep quality and especially the deep sleep phase. Shortening and disrupting the deep sleep phase increases the risk of death from a wide variety of diseases ( 5 ) ( 6 ).