What Your Shopping Bag May Mean for Your Health

Shoppers who used reusable grocery bags bought more junk food

Do you BYOB? Bring your own bags, that is. If you do, you may wind up treating more than just the environment.

A new study found that, when shoppers brought their own resuable bags to the store, they tended to buy more organic products — but also more junk food.

"As concerns about pollution and climate change become more mainstream, the belief that shopping with reusable grocery bags is an important environmental and socially conscious choice has gained prevalence," wrote study authors Uma R. Karmarkar, PhD, of Harvard University, and Bryan Bollinger, PhD, of Duke University. "However, little is known about how these initiatives might alter other elements of consumers' in-store behavior."

Drs. Karmarkar and Bollinger looked at data from about 140,000 shopping trips to a single grocery store in California in the mid-2000s. This data was collected using loyalty card information and surveys.

Those shoppers who brought their own bags were 13 percent more likely to buy organic products. However, they were also 7 percent more likely to buy junk foods like chips or cookies.

According to Drs. Karmarkar and Bollinger, the connection between using reusable bags and buying organic foods was a fairly easy one to uncover — because most consumers who bring these bags consider themselves to be helping the environment.

In the case of junk foods, these results may be chalked up to what’s called the “licensing effect.”

The "licensing effect" is a phenomenon that occurs when a person makes a decision that could be called 'responsible' or 'noble.' As a result, that person may feel entitled to a little reward.

The parents in the group, however, did not change their shopping habits just because they brought reusable bags.

The researchers said that this might be because parents are focused on their kids’ needs rather than their own.

“In short, bringing your own bags changes the way you shop," Drs. Karmarkar and Bollinger wrote. "Our findings thus have important implications for grocery store managers. In stores where reusable bags are popular, marketing organic or sustainably farmed foods as indulgences could increase the sales of those items.”

This study was published in the July issue of the Journal of Marketing.

No funding sources or conflicts of interest were disclosed.