Can’t resist that rich, chocolatey milkshake? No use trying to say no to gooey cheese fries?

Researchers writing in the journal Nature Communications may have figured out one reason why. They say they’ve identified a brain pathway with a role in whether we eat and drink impulsively.

Experimenting with rats, the scientists tinkered with levels of a hormone called melanin-concentrating hormone, or MCH for short. Specifically, they were working with neurons that connect to receptors in the hippocampus.

They found that impulsivity increased whether MCH output along the pathway went up or down. The animals’ taste for food or willingness to work for it did not change. It was just that the rats were more impulsive in seeking food.

How can one tell if a rat is acting impulsively? Good question. In this experiment, the rats could get a piece of high-fat, high-sugar food by pressing a lever no more than every 20 seconds. Pushing the lever more frequently meant a longer wait for food to arrive.

Rats with abnormal MCH output tapped the lever more frequently, even though they had learned previously to wait 20 seconds. This was an example of impulsive behavior by the rat. He knew that frequent presses would not ultimately be of benefit. But, he just couldn’t help himself.

Perhaps this sounds familiar to you. People realize impulsivity about food consumption can harm in the long run, but sometimes we just can’t bring ourselves to say no.

The study authors say a medication regulating MCH may one day help people struggling with obesity. Maybe someday, willpower in a pill will help us all stay skinny.