A lack of light, dreamy slumbers known as rapid eye movement (REM) sleep might be triggering a craving for sweet and fatty foods among sleep-deprived individuals, a team of scientists found.

The study on mice by Michael Lazarus, an associate professor of sleep medicine at the University of Tsukuba, Kristopher McEown, a project assistant professor at the University of Tokyo, and others could help to explain the high obesity rates among people with sleep deprivation.

According to other studies, people with sleep deprivation are prone to obesity because they tend to consume large amounts of food with high calories. But why this happens has been a mystery.

The research team sought to solve this question by exploiting a tendency in mice: their REM sleep decreases significantly in an unstable sleeping environment in which the bottom of their cage is lined with a wire mesh grid.

When these REM sleep-deprived mice were given a choice of several food items with different flavors, they consumed 30 percent more sweet food containing large amounts of sucrose and fatty food with a high lipid content than those in the control group with normal sleeping patterns.

The same experiment was repeated on mice that were genetically engineered to inhibit activity in their prefrontal cortex, the part of the brain that identifies smell and taste.

When deprived of REM sleep, these mice still consumed many fatty foods but did not eat excess amounts of sweet stuff.

From these observations, the scientists concluded that people who lack sleep often crave sweets because of a mechanism triggered by this part of the brain.

Lazarus said that the exact reason for this phenomenon remains unclear, but he believes that the overall sleep deprivation leads to a lack of REM sleep, which can prompt obesity.

“The study is highly intriguing because it is epidemiologically true that there are many with obesity among short-sleepers, but the exact neural mechanism that transforms one’s eating habits and leads to obesity remained unsolved,” said Kazuo Mishima, a department head at the National Institute of Mental Health, who was not part of the study.

“As the amount of deep sleep does not decrease among the sleep-deprived, but the REM and light non-REM sleep levels do, we anticipate seeing further research that identifies the effects of those tendencies as well,” he said.

The study was published in the British scientific journal eLife in December.