Ever wondered why those donuts in your office look so appetizing first thing in the morning? New research shows we’re more likely to crave unhealthy foods when we’re tired.

Researchers from St. Luke’s-Roosevelt Hospital Center in New York City and Columbia University worked with 25 healthy-weight adults after those people were allowed to sleep either four or nine hours at night.

They found the sleep-deprived volunteers ate 300 daily calories more than their well-rested cohorts, and chose fattier foods, too.

Principal investigator Marie-Pierre St. Onge also said brain scans on the sleepy participants showed the brain regions involved with reward, pleasure and addiction were more activated by the sight of unhealthy foods like donuts, cake, bacon cheeseburgers, pepperoni pizza and candy.

Scientists hope their work could help explain the link between a lack of sleep and an elevated risk for obesity. But there’s also an immediate take-away for the rest of us.

“If you’re trying to control your weight … it’s better not to be sleep-deprived,” Dr. St. Onge said. “You have a hormonal and neuronal network that sets you up [to] succumb to sights of unhealthy foods.”

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