We’ve all been there. You go to the grocery store after a long gym session or a hard day at work and instantly grab many items off the shelves. You’re starving, maybe even hangry — the new amalgam of hungry and angry.

It turns out there’s a scientific explanation for finding food irresistible in such moments. Researchers in Sweden have found that a hunger-driven hormone interferes with the ability to make a rational decision. The hormone, called ghrelin [ɡrɛlɪn], causes more impulsive actions. It’s produced in the gastrointestinal tract and released on an empty stomach. The findings were published recently in the journal Neuropsychopharmacology.

During the study, researchers trained rats to perform tasks that would allow the scientists to measure impulsive behavior. For example, the rats were trained to either press a lever to get an instant reward, or they were rewarded later for not pressing the lever. During each trial, ghrelin was given to some of the rats. The hormone made the animals three times more likely to press the reward lever in all of the trials, which was categorized as impulsive behavior.

The researchers hope their findings will help with the development of new drugs, such as ghrelin-blocking medications, to treat obesity. They also believe that further research with ghrelin could help target the treatment of psychiatric disorders, such as attention deficit hyperactivity disorder, that are marked by impulsive behavior. The hormone’s powerful effect goes beyond hunger: It has also been implicated in the reward behavior associated with drugs and alcohol.

So the next time you have to make a big decision, you might want to make sure you do it on a full stomach.