As the ban on plastic bags is in effect in many U.S. cities, shoppers usually opt to bring their own reusable bags to do their grocery shopping, but a new study has shown that doing such has some implications to a person's choice when it comes to buying food.

Researchers from the Harvard Business School said that shoppers are 13 percent more likely to put organic items inside their reusable bags. While this may be good, they are also seven percent likely to buy chips and cookies along with it.

"It was clear that shoppers who brought their own bags were more likely to replace nonorganic versions of goods like milk with organic versions. So one green action led to another. But those same people were also more likely to buy foods like ice cream, chips, candy bars, and cookies. They weren't replacing other items with junk food, as they did with organic food. They were just adding it to their carts," said Uma Karmarkar, one of the researchers, according to Harvard Business Review.

The researchers studied two years' worth of transaction data from a grocery store located in California and also did a poll of a select group of participants. They asked the shoppers why they had their own bags and found out that many of them exhibited what is called the "licensing effect." "It's the same thing as when someone says, 'I exercised this morning, I deserve a dessert at dinner,'" said Bryan Bollinger, the co-author from Duke University, via Today.

The study authors also theorized that many shoppers with reusable bags think they are doing good for the environment, hence triggering their desire to purchase more organic food despite not exactly knowing what real organic and healthy consists.

The researchers, however, said that they found out that shopping habits differ with parents, regardless if they have their own grocery bags or not. They theorized that the parents' purchasing decision are not triggered by their own indulgences or healthy choices, but rather, the needs of the kids.

The study was published in the journal American Marketing Association.