And when the participants in that study were switched to a healthier diet, their sleep quality improved.“Both poor diet and poor sleep increase the risk of several public health conditions.”
The researchers asked 15 healthy young male volunteers to follow a healthy diet, and an unhealthy diet, in a random order for one week. Each diet contained roughly the same amount of calories. The unhealthy diet contained nearly double the amount of fat — 44% versus 23% — of the healthy diet, and almost double the amount of sugar, too .
But after eating an unhealthy diet, during a deep sleep stage of rest, the amount of slow-wave activity in the men’s brains was reduced. Slow-wave brain activity is one measure of how restorative sleep is, and insulin sensitivity and the secretion of growth hormones have been linked to slow-wave sleep.“Intriguingly, we saw that deep sleep exhibited less slow-wave activity when the participants had eaten junk food, compared with consumption of healthier food.