I have read before that tiredness can mimic hunger but new research may prove the deeper reason behind the connection between lack of sleep and poor eating habits. According to a new university report, sleep deprivation can increase cravings for junk food, more over a sleepless night makes us more likely to reach for doughnuts or pizza than for whole grains and leafy green vegetables, the U.S. study suggests.

The study at the University of California, Berkeley, examined the brain regions that control food choices and researchers say the findings shed new light on the link between poor sleep and obesity.

Using functional magnetic resonance imaging (fMRI), 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.

In this newest study, 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.

On a positive note, Professor Walker said, 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’.