WEDNESDAY, March 14,, 2007 (HealthDay News) -- The grocery lists most people jot down before going to the store can create a mental loophole for impulse food.
That's because the act of remembering a variety of food choices makes people more vulnerable to slipping cookies, chips and other not-so-healthy items onto the list, a new study finds.
"The mental effort that you're using is mental effort you do not have to keep yourself in check -- controlling your desire for chocolate cake rather than fruit salad, for example," explained lead researcher Yuval Rottenstreich, an associate professor of management at Duke University.
Rottenstreich stressed, however, that it was still smarter to head to the supermarket with a list in hand than without -- just read it back and cross out any sugary or fatty items that may have snuck in.
The study is published in the March issue of the Journal of Consumer Research.
For years, nutritionists have urged dieters to draw up healthy, calorie-conscious shopping lists before they head out to the supermarket. "Not having that security of a shopping list ahead of time could actually be quite negative, especially if the person is going through the supermarket hungry," said Bonnie Taub-Dix, a New York City-based registered dietitian and spokeswoman for the American Dietetic Association.
The advice makes intuitive sense, but Rottenstreich and his co-researchers wanted to test whether it was foolproof in keeping folks true to their goals.
In three separate experiments, college students were asked to make consumer choices based on two real-life paradigms: "stimulus-based" decision-making, where the objects to choose from were right in front of the student (as would happen in a supermarket), and "memory-based" decision-making, where the students were asked to list the things they wanted to buy by drawing on their memory.
Lists didn't perform quite as well as expected.
In one experiment centered on a choice of four desserts -- chocolate cake, cheesecake, creme, and fruit salad -- the participants chose the healthier fruit salad far more when the four items were presented to them than when asked to recall the desserts from memory and then list their preference.
According to Rottenstreich, "This points out that making a list from memory does have a bit of a downside." The finding, he said, can be explained by neurology: The human brain does not have the capacity to activate both working memory and a full complement of rational impulse-control at once.
"So, if I am spending mental effort formulating my list, then that is mental effort I do not have in terms of making sensible choices," said Rottenstreich, who helped conduct the study while at New York University. In those situations, choices become more emotional, so tempting (but calorie-rich) "mistakes" can slip in.
But that doesn't mean dieters should throw out their grocery lists.
"I'd say that lists do work, in lots of ways. We're just aware now that there are trade-offs," Rottenstreich said. The simple act of re-reading your grocery list and crossing out any high-fat, high-sugar items can eliminate the problem, he added.
Taub-Dix agreed that drawing up a grocery list is a great way to keep unhealthy foods out of the home. She has even come up with a means of streamlining the process that's less taxing on the memory.
"I actually have a master list that I have typed out that's more or less the layout of my supermarket," she said. "On it, I will put all my fresh fruits and vegetables listed first, then the deli, etcetera. Then I just print it out and circle what I need. It makes shopping so much easier."
Another tip: Try and stick, whenever possible, to the supermarket's outside perimeter. "That's where the fresh produce, fruits and vegetables, the dairy aisle, chicken and lean meats usually are," Taub-Dix said.
And don't ever shop when you're hungry.
"We know that when you are too hungry, it's like being too tired or too drunk," she said. "What comes from that is apathy -- 'Whatever, I'm just going to take this.' "
A separate study, published in the same issue of the journal, suggests that the human mind finds other ways to get around self-control. In some cases, suppressing one area of mental or behavioral activity spurs an excess of activity in another area, such as spending.
In the study, researchers at the University of Minnesota asked half of the participants to perform a mental task but to not think of a "white bear." Then they gave the participants $10 to spend at a bookstore. The shoppers could keep any unspent money for themselves.
The result: People who had tried to stop themselves from thinking about the "white bear" spent an average of $4.05 -- nearly three times as much ($1.21) as participants who were put under no such constraint.
The finding may have lessons for people who embark on regimens involving self-denial, the researchers said. Perhaps, they wrote, "people should avoid shopping on days when they have earlier exercised great self-control or when starting a new self-improvement program, such as a new diet."
There's more on healthy eating at the American Dietetic Association.