If you often find yourself craving food you know you don't need your sleeping habits could be to blame.
Researchers from the University of Chicago found that sleep deprivation initiates the body's endocannabinoid system - the same system targeted by marijuana that enhances the joy of eating and increases hunger.
The team found that people were more likely to crave junk food including crisps and chocolate when sleep deprived rather than healthy food, which could lead to weight gain if consumed regularly.
The volunteers were monitored in two situations: one four-day stay in the University’s Clinical Research Centre during which they spent 8.5 hours in bed each night (averaging 7.5 hours of sleep), and another four-day stay when they spent only 4.5 hours in bed (averaging 4.2 hours of sleep).
The participants ate identical meals three times each day, at 9am, 2pm, and 7pm.
Sleep deprived participants expressed greater desire to eat than those who had gotten enough shut-eye. When asked, tired participants estimated that they could eat much more than they predicted the day after a full night’s sleep.
After the fourth night of restricted sleep, subjects were offered an array of snack foods.
Despite having eaten a large meal less than two hours before being offered snacks, those in the restricted sleep phase of the study had trouble limiting their snack consumption. They chose foods that provided 50% more calories, including twice the amount of fat, as when they were completing the normal sleep phase.
"We found that sleep restriction boosts a signal that may increase the hedonic aspect of food intake, the pleasure and satisfaction gained from eating," study lead Erin Hanlon said in a statement.
"Sleep restriction seems to augment the endocannabinoid system, the same system targeted by the active ingredient of marijuana, to enhance the desire for food intake."
She added: "If you have a Snickers bar, and you’ve had enough sleep, you can control your natural response.
"But if you’re sleep deprived, your hedonic drive for certain foods gets stronger, and your ability to resist them may be impaired. So you are more likely to eat it. Do that again and again, and you pack on the pounds."
The full study is published in the journal SLEEP.