Junk food can disrupt deep sleep

If you don’t sleep well, you tend to eat too much fat and too much sugar afterwards. But does diet also affect sleep? In fact, a high-fat, high-sugar meal in the evening seems to impair the quality of deep sleep.

junk food disrupts sleep


Junk food has become increasingly prevalent in modern diets, with its high levels of sugar, unhealthy fats, and processed ingredients. While the negative impact of junk food on physical health is well-known, its effects on sleep have gained attention in recent years. Emerging research suggests that consuming junk food can disrupt deep sleep, affecting overall sleep quality and potentially leading to various health consequences. This article aims to explore the relationship between junk food consumption and its disruptive effects on deep sleep.

Understanding Deep Sleep

Deep sleep, also known as slow-wave sleep or stage 3 non-rapid eye movement (NREM) sleep, is a crucial stage of the sleep cycle. During this stage, the body experiences slow brain waves and various restorative processes occur. Deep sleep plays a vital role in memory consolidation, hormone regulation, immune function, and overall physical and mental restoration.

Impact of Junk Food on Sleep

Junk food consumption has been linked to several factors that can disrupt deep sleep.

  1. Sugar and Insulin Spikes: Junk foods often contain high levels of added sugars, leading to rapid spikes in blood sugar levels. This triggers the release of insulin, which can interfere with the body’s ability to achieve and maintain deep sleep, disrupting the sleep cycle.
  2. Unhealthy Fats: Trans fats and saturated fats found in many junk foods have been associated with poor sleep quality. These fats can increase inflammation in the body, affecting sleep patterns and leading to sleep disturbances.
  3. Gastrointestinal Discomfort: Junk foods are typically low in fibre and high in processed ingredients, which can cause digestive issues such as acid reflux, indigestion, and discomfort. These gastrointestinal disturbances can disrupt sleep and prevent the body from entering deep sleep stages.
  4. Stimulants: Certain junk foods, such as those containing high levels of caffeine or artificial stimulants, can interfere with sleep onset and disrupt the natural sleep-wake cycle.

Ready pizza against salmon and vegetables

Researchers from Uppsala University recruited 15 healthy young men for their experiment. They were randomly assigned either a healthy or a more unhealthy eating plan to follow for a week. Then they switched to the other variant.

During the unhealthy week, participants ate junk food meals high in saturated fat and sugar, such as pizza, packaged meatballs, or chocolate wafers.

The healthy weekly schedule included meals that were low in fat and sugar but high in fibre, such as unsweetened muesli and yoghurt, and salmon with vegetables.

The calorie content was the same in both nutrition weeks and adapted to the needs of the respective participant. After a week they switched. At the end of each week, the test subjects spent two nights in a sleep laboratory, which allows for a precise analysis of the sleep phases.

No difference in sleep duration

The result: “We found that the participants slept for the same amount of time on both diets,” explains Jonathan Cedernaes, Professor of Medical Cell Biology at Uppsala University. And also with the length of the different sleep phases – deep, light and dream sleep (REM -sleep) – the researchers could not find any differences.

However, the detailed analysis of deep sleep, of which one goes through several phases every night, revealed serious deviations. They are crucial for physical and mental recovery: During this time, the body releases growth hormones, breaks down the stress hormone cortisol, and newly learned things are hardened in the memory.

Less restorative deep sleep

“Specifically, we looked at slow brain wave activity, a measure of how restorative deep sleep is,” explains Cedernaes. “Interestingly, we found that slow wave activity during deep sleep was lower when participants ate junk food than when they ate healthier foods.”

The researchers cannot yet say how long the effects of an unhealthy diet on sleep last. It is also unclear which components of junk food disrupt deep sleep – and through which mechanisms this happens. “It would also be interesting to check whether the shallower deep sleep impairs certain functions that are regulated in this sleep phase,” says Cedernaes.

Mediterranean diet for bad sleep?

Similar changes in sleep observed here also occur with age and insomnia. Diet could possibly play a greater role in sleep problems than previously assumed, the doctor suspects.

For example, you can rely on the Mediterranean diet – it is based on a lot of plant-based food, healthy oils, fish and nuts on the one hand and on little saturated fats, white flour and sugar on the other. You can never go wrong with this diet: in particular, its positive effect on cardiovascular health has already been proven in many large-scale studies.

Research Findings

Recent studies have provided insights into the relationship between junk food consumption and disrupted deep sleep. A study published in the journal Nutrients found that a diet high in saturated fat and added sugars was associated with more awakenings during the night and less time spent in deep sleep. Another study published in the American Journal of Clinical Nutrition revealed that greater consumption of fast food and sweets was linked to shorter sleep duration and poorer sleep quality.

Promoting Healthy Sleep Habits

To mitigate the negative effects of junk food on deep sleep and overall sleep quality, adopting healthy sleep habits is crucial:

  1. Balanced Diet: Opt for a balanced diet rich in whole foods, including fruits, vegetables, whole grains, lean proteins, and healthy fats. This promotes overall health and can positively impact sleep quality.
  2. Mindful Eating: Practice mindful eating by being aware of portion sizes and choosing nutritious options over processed junk foods.
  3. Time of Consumption: Avoid consuming heavy or high-sugar foods close to bedtime. Allow sufficient time for digestion before sleep.
  4. Hydration: Stay hydrated throughout the day but avoid excessive fluid intake before bedtime to prevent frequent bathroom trips that can disrupt sleep.
  5. Regular Exercise: Engage in regular physical activity, as it can improve sleep quality and help regulate sleep patterns.

Studies conducted in various countries have provided insights into the relationship between junk food consumption and sleep quality:

  • United States: Research in the United States has revealed a significant association between increased consumption of junk food and poor sleep quality, including shorter sleep duration and more frequent awakenings during the night.
  • United Kingdom: Studies in the United Kingdom have highlighted the negative impact of junk food on sleep quality, with higher consumption of fast food and sugary snacks correlating with shorter sleep duration and increased sleep disturbances.
  • Australia: Similar findings have been observed in Australia, where a higher intake of junk food has been linked to reduced sleep quality and an increased risk of insomnia symptoms.
  • India: Studies conducted in India have reported an association between the consumption of unhealthy food choices and sleep disturbances, suggesting that junk food may have a negative impact on sleep quality in this cultural context as well.
  • United Arab Emirates: Although specific studies on the relationship between junk food and sleep quality in the UAE are limited, it can be inferred from global research that similar associations may exist. Studies conducted in other countries have demonstrated the negative impact of junk food on sleep quality, including shorter sleep duration, increased sleep disturbances, and reduced deep sleep stages.


While the convenience and taste of junk food may be tempting, it is essential to recognize the potential negative impact on sleep, particularly deep sleep. Consuming junk food can disrupt the sleep cycle and compromise overall sleep quality. By adopting a balanced diet, practicing mindful eating, and prioritizing healthy sleep habits, individuals can optimize their sleep and promote overall well-being. Making informed choices and prioritizing nutritious foods can contribute to better sleep patterns and long-term health.