A diet centered on pizza and chocolate changed brain activity during sleep
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Eating a diet high in fat or sugar can disrupt the brain’s electrical activity during deep sleep and reduce sleep quality.
When we sleep, electrical activity in the brain slows down. Higher frequency brain waves, called beta waves, dominate during our waking hours, gradually being replaced by lower frequency brain waves, called delta waves.
The deepest and most restorative stage of sleep, called slow-wave sleep, has the highest percentage of delta waves. This usually occurs in the first half of the night, when the body repairs itself and consolidates memories.
Jonathan Sedernes of Uppsala University, Sweden, and colleagues tested the effect of a Western-style high-fat, high-sugar diet on slow-wave sleep in 15 men with an average age of 23.
Men were randomly assigned to a high-fat, high-sugar diet or a low-fat, low-sugar diet for one week. They then wore electroencephalography (EEG) caps and slept overnight in the lab to record their brain’s electrical activity. After a few weeks of rest, they switched to other diets and repeated the sleep study in the lab.
Participants were provided with all meals and had to eat at set times. The high-fat, high-sugar diet included foods such as sweetened granola, pizza, and chocolate, but…
A low-fat, low-sugar diet included foods such as sugar-free muesli, salmon, and vegetables. The calories of the two meals matched.
Each man typically slept for the same amount of time on the two diets and felt the quality of sleep was the same.
However, electroencephalograms suggest that a high-fat, high-sugar diet interferes with slow-wave sleep by decreasing the proportion of delta waves and increasing beta waves, resulting in poor rest. This occurred in his 11 of his 14 men for whom full results were collected.
This effect may be because sugar and fat activate pathways in the brain that increase alertness, but more research is needed to understand the mechanism, Sedernes said. She also wants to repeat the study to see if this change occurs in women as well.
Although the long-term effects of interfering with slow-wave sleep in this way are unknown, we do know that poor diet leads to poor health in general, partly because it affects sleep quality. Effects could explain it, he says.
Because the amount of slow-wave sleep naturally declines with age, it may be particularly important for older adults to eat a healthy diet to prevent further deterioration of sleep quality, Sedernes said.
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