Scientists found that when normal weight volunteers looked at unhealthy food during a period of sleep restriction, the reward centers in their brains were more active than when they looked at the pictures after having slept regularly.

The researchers, from St Luke’s – Roosevelt Hospital Center and Columbia University in New York, were using functional magnetic resonance imaging (fMRI) to better understand the link between sleep restriction and obesity.

They compared brain scans of 25 male and female volunteers when they were shown images of healthy and unhealthy foods after five nights of sleep restriction (no more than four hours of sleep a night) and regular sleep (up to 9 hours a night).

The unhealthy foods included nutrient poor foods such as candy and pepperoni pizza, and the healthy foods included nutrient rich foods such as oatmeal, fruits and vegetables.

The study findings were presented last weekend at SLEEP 12, the 26th annual meeting of the Associated Professional Sleep Societies (APSS) in Boston.

Principal investigator Dr Marie-Pierre St-Onge, a Research Associate with the New York Obesity Research Center, told the press:

“The same brain regions activated when unhealthy foods were presented were not involved when we presented healthy foods.”

“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,” she added.

St-Onge said the findings support the idea that insufficient sleep affects appetite regulation and obesity.

Previous studies have already shown that restricted sleep makes people tend to eat more, and that people report a greater desire for sweet and salty food when they have been sleep-deprived.

The study also showed that participants ate more overall and ate more fat after restricted sleep than they did after regular sleep.

Funds from the National Institutes of Health (NIH) helped pay for the study.