by Yasmin Anwar, UC Berkeley
August 14, 2013 (TSR) – A sleepless night makes us more likely to reach for doughnuts or pizza than for whole grains and leafy green vegetables, suggests a new study that examines the brain regions that control food choices.
The findings shed new light on the link between poor sleep and obesity.
Using functional magnetic resonance imaging (fMRI), UC Berkeley researchers scanned 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 centers that respond to rewards. Moreover, the participants favored 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,” says Matthew Walker, professor of psychology and neuroscience at the University of California, Berkeley.
“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.
“These results shed light on how the brain becomes impaired by sleep deprivation, leading to the selection of more unhealthy foods and, ultimately, higher rates of obesity,” says doctoral student Stephanie Greer, the study’s lead author.
For this study, published in Nature Communications, 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 more popular choices following a sleepless night.
On a positive note, Walker says, the findings indicate that “getting enough sleep is one factor that can help promote weight control by priming the brain mechanisms governing appropriate food choices.”