A sleepless night can make you more likely to crave junk food, according to a new study.
Researchers from University of California, Berkeley used functional magnetic resonance imaging (fMRI) to scan the brains of 23 healthy young adults, first after a normal night's sleep and next, after a sleepless night.
They found impaired activity in the sleep-deprived brain's frontal lobe, which governs complex decision-making, but increased activity in deeper brain centres that respond to rewards.
Moreover, the participants favoured unhealthy snack and junk foods when they were sleep deprived.
"What we have discovered is that high-level brain regions required for complex judgments and decisions become blunted by a lack of sleep, while more primal brain structures that control motivation and desire are amplified," said Matthew Walker, a UC Berkeley professor of psychology and neuroscience and senior author of the study.
Moreover, he added, "high-calorie foods also became significantly more desirable when participants were sleep-deprived. This combination of altered brain activity and decision-making may help explain why people who sleep less also tend to be overweight or obese."
Previous studies have linked poor sleep to greater appetites, particularly for sweet and salty foods, but the latest findings provide a specific brain mechanism explaining why food choices change for the worse following a sleepless night, Walker said.
In the study, researchers measured brain activity as participants viewed a series of 80 food images that ranged from high-to low-calorie and healthy and unhealthy, and rated their desire for each of the items. As an incentive, they were given the food they most craved after the MRI scan.
Food choices presented in the experiment ranged from fruits and vegetables, such as strawberries, apples and carrots, to high-calorie burgers, pizza and doughnuts. The latter are examples of the more popular choices following a sleepless night.
The study was published in the journal Nature Communications.
