When you buy groceries, do you pay with plastic? Try forking over cold cash instead. Reason: In an era in which both the obesity rate and credit/debit card usage are climbing, paying cash could boost your willpower and reduce the allure of junk foods. I heard from Manoj Thomas, PhD, an assistant professor of marketing at Cornell University.

Previous research revealed that using cash increases the “pain of payment”—in other words, physically handing over actual dollar bills feels worse than simply swiping a credit or debit card—and that payment method affects consumers’ willingness to spend money, particularly on impulsive purchases. Dr. Thomas led a new study, published in the Journal of Consumer Research, that analyzed six months’ worth of supermarket purchases made by 1,000 shoppers, the majority of whom switched back and forth between card and cash payments.

Findings: On the occasions when they paid cash, shoppers were significantly less likely to buy unhealthful “vice” foods (cookies, cakes, pies)—which tend to be selected on impulse—than when they paid with plastic. Paying cash did not reduce the purchase of healthful “virtue” foods (oatmeal, fat-free yogurt, whole-wheat bread), which generally are selected with more deliberate intention.