New research shows why people often succumb to junk food when sleep-deprived.
In one new study, experts discovered the sight of unhealthy food stimulates specific brain centers more when we have inadequate sleep, as compared to when an individual has sufficient sleep.
Researchers from St. Luke’s – Roosevelt Hospital Center and Columbia University in New York performed functional magnetic resonance imaging (fMRI) on 25 men and women of normal weights while they looked at images of healthy and unhealthy foods.
The scans were taken after five nights in which sleep was either restricted to four hours or allowed to continue up to nine hours. Results were compared.
“The same brain regions activated when unhealthy foods were presented were not involved when we presented healthy foods,” said Marie-Pierre St-Onge, Ph.D., the study’s principal investigator.
“The unhealthy food response was a neuronal pattern specific to restricted sleep. This may suggest greater propensity to succumb to unhealthy foods when one is sleep restricted.”
Previous research has shown that restricted sleep leads to increased food consumption in healthy people, and that a self-reported desire for sweet and salty food increases after a period of sleep deprivation.
St-Onge said the new study’s results provide additional support for a role of short sleep in appetite-modulation and obesity.
“The results suggest that, under restricted sleep, individuals will find unhealthy foods highly salient and rewarding, which may lead to greater consumption of those foods,” St-Onge said.
“Indeed, food intake data from this same study showed that participants ate more overall and consumed more fat after a period of sleep restriction compared to regular sleep. The brain imaging data provided the neurocognitive basis for those results.”
In a related study, 23 healthy adults were scanned at two different periods, one after a normal night’s sleep and a second after a night of sleep deprivation. In both sessions, participants rated how much they wanted various food items shown to them while they were inside the scanner.
“Our goal was to see if specific regions of the brain associated with food processing were disrupted by sleep deprivation,” said lead author Stephanie Greer, a doctoral student in neuroscience at the University of California, Berkeley.
Investigators determined that sleep deprivation significantly impaired brain activity in the frontal lobe, a region critical for controlling behavior and making complex choices, such as the selection of food to eat.
The finding confirms research that suggests that sleep loss may prevent the higher brain functions from making appropriate food choices, rather than necessarily changing activity in deeper brain structures that react to basic desire.
“We did not find significant differences following sleep deprivation in brain areas traditionally associated with basic reward reactivity,” Greer said. “Instead, it seems to be about the regions higher up in the brain, specifically within the frontal lobe, failing to integrate all the different signals that help us normally make wise choices about what we should eat.”
She added that this failure of the frontal lobe to optimally gather the information needed to decide on the right types of foods to eat – such as how healthy relative to how tasty an item may be – may represent one brain mechanism explaining the link between sleep loss and obesity.
“These results shed light on how the brain becomes impaired by sleep deprivation, leading to improper food choices,” Greer said.