Why Do Sleepy Brains Crave Doughnuts?

We’re more likely to have an appetite for junk food when we’re sleep deprived and brain scans may help explain why.

Using functional magnetic resonance imaging (fMRI), researchers scanned the brains of 23 healthy young adults, first after a normal night’s sleep and then 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.  When they were sleep-deprived, participants favored unhealthy snacks and junk food. 

“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, 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.

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