Research published in the Journal of Neuroscience unveils an important link between sleep deprivation and junk food consumption, showing that sleep-deprived persons were willing to pay more for a food snack than their rested counterparts.
Previous studies had suggested that lack of sleep was connected to expanding waistlines, with some pointing towards changing hormone levels due to disrupted sleep as a determinant of how full or hungry people felt. But the latest research suggests that that the leading cause could be the interaction within and between reward recognition systems in the brain.
Describing the study design, Prof Jan Peters and his colleagues from the University of Cologne describe how they recruited 32 healthy men aged between 19 and 33 and gave all of them the same dinner of pasta and veal, an apple and strawberry yoghurt. After that, participants were either sent home wearing sleep tracking devices or kept awake all night in the laboratory.
The next morning, all returned to have their appetite rated and 29 of them had their blood sugar and stress-linked hormones measured. They took part in a game which asked how much they would be willing to pay for 24 snack foods and 24 inedible foods on a scale of €0-€3.
Using a functional magnetic resonance imaging (fMRI) scan, they were asked to choose whether or not they would buy the object when its price was fixed, allowing researchers to look a participants’ brain activity upon seeing food. The process was repeated a week later, with sleep-deprived participants being allowed to sleep, and vice versa.
The fMRI results showed that participants had greater activity in the brain’s amygdala (which processed food rewards) when food images were shown and a stronger correlation between the price they would pay and the activity in the hypothalamus (which regulates consumption) when they were sleep deprived.
The team also found no link between changes in levels of des-acyl ghrelin and any part of the brain or behaviour differences, although that could be because the levels were very high. The team said that this suggested changes in brain activity in response to food images were not just about hormones.
Christian Benedict, a neuroscientist at Uppsala University in Sweden who was not involved in the study, welcomed the research saying that when individuals were sleep deprived, their brains used more energy and it made sense that the brain would promote signals that increase food consumption, instead of wasting energy on controlling impulses. He also noted that the research had limitations, including the fact that it was small and blood was not taken when participants were viewing images of food during scanning and the study did not record responses to healthy food.
He said it was important to remember that many factors besides sleep can affect body weight. “It is not only about sleep. Physical activity matters, dietary things, food and accessibility. So we should not break it down only to sleep.