Eating unhealthy for a few days? Your sleep might already be aging, says study

Initially, the participants were assessed on their sleep-related habits, which ought to be within the recommended range: an average of seven to nine hours of sleep per night.

The participants were given a healthy and less healthy diet in a random sequence. Both diets contained the same number of calories, adjusted to the daily needs of each individual. The unhealthy diet consisted of higher quantities of sugar, saturated fats, and processed foods.

The meals were consumed at times customized to each individual's schedule. Each participant followed each diet plan for a week.

Participants' brain activity was monitored while they slept in the lab.

"We noted that the participants slept the same amount of time under both diets. Additionally, with both diets, participants spent the same amount of time in different stages of sleep. However, we were particularly interested in studying the properties of their deep sleep." explained Dr. Jonathan Cedernaes, associate professor of medical cell biology at the University of Uppsala.

"We specifically observed the slow-wave activity, which indicates rejuvenating, deep sleep. We found that deep sleep showed less slow-wave activity when participants ate unhealthy food. This effect continued through the second night. Essentially, an unhealthy diet resulted in a lighter form of 'deep sleep'. It's important to note that similar changes in sleep happen with age and conditions such as insomnia," the researcher added.

He clarified that until now, no studies have been directed toward isolating the effects of varying diets on sleep.

"Sleep is the outcome of various physiological states' interaction. However, until this point, it hasn't been explored how diet quality impacts sleep quality in the same set of healthy people. It's intriguing to find out that sleep quality is highly dynamic and the depth and phases of sleep can also be influenced by diet." Dr. Cedernaes elaborated.

Scientists are currently unsure of the longevity of the sleep effects associated with an unhealthy diet. They also don't fully understand which substances in an unhealthy diet degrade the quality of deep sleep.

"We aim to determine whether there is a unique molecule that plays a significant role in this. Our dietary intervention was also quite brief, and both the sugar and fat content could have been higher. It's possible that a worse diet would have an even more notable effect on sleep," highlighted Dr. Cedernaes.