Remember your mother’s advice not to go grocery shopping when you’re hungry? Well, newly published research suggests her wise warning didn’t go far enough.

It implies the famished shouldn’t go shopping at all.

A research team led by Alison Jing Xu of the University of Minnesota reports that hunger “is likely to activate general concepts and behavioral knowledge associated with acquisition,” making one more likely to purchase even non-food products.

It appears that, when tempted by things to buy, the internal message “I want food” gets pared down to simply “I want.”

A growling stomach doesn't increase the appeal of these inedible items; rather, it appears to activate a need to acquire something, anything. So if you shop while hungry, don’t be surprised if you come home, open your bag and ask, "What was I thinking when I bought this?"

In the Proceedings of the National Academy of Sciences, Xu and her colleagues describe five studies that support this proposition. In two of them, the participants (89 and 63 undergraduates, respectively) examined binder clips from Staples, and were told they could take home with them as many as they’d like.

In the first study, the students reported how hungry they felt. In the second, the researchers made sure some were hungrier than others by having them engage in a purported “taste test” of a loaf cake before checking out the office supplies.

In both cases, hunger did not influence their evaluation of the binder clips. But also in both cases, the hungry participants took significantly more of the binder clips than the satiated ones.

Another experiment was performed in a real-world setting: A large department store. Researchers approached 81 shoppers who were leaving the facility. With their permission, they scanned their receipts as the shoppers filled out a short questionnaire that included a question about how hungry they were.

The results: Hungry shoppers spent more money, and bought more (non-food) products, than less-hungry ones. This remained true after taking into account such factors as their mood and how much time they had spent in the store.

It all suggests that “a basic biologically based motivation”—the desire to eat—“can affect substantively unrelated behaviors,” the researchers conclude. It appears that, when tempted by things to buy, the internal message “I want food” gets pared down to simply “I want.”

So if you must head for the mall on an empty stomach, it might be a good idea to begin with a quick stop at the food court. Granted, it may be expand your waistline, but it may also prevent that dreaded disease known as shrinking wallet syndrome.