Grocery Shopping When Hungry

Grocery shoppers bought more high calorie foods when hungry than when full

(RxWiki News) Grocery shopping on an empty stomach may lead to different food choices. Buying candy and salty snacks may be easier to resist on a full stomach.

In a recent study, researchers followed a group of people to see what types of foods they bought at a grocery store when they were hungry versus when they were full.

The results of the study showed that people purchased more high-calorie foods when they were hungry compared to when they were not hungry, and fewer low-calorie foods when they were hungry compared to when they were not hungry.

"Eat a healthy snack before grocery shopping."

Aner Tal, PhD, a post-doctoral fellow, and Brian Wansink, PhD, professor in the Dyson School of Applied Economics & Management at Cornell University in Ithaca, NY, worked on a study to investigate what people buy at the grocery store when they haven't eaten in a while.

According to these researchers, people may fast (consuming no solid food for an extended period of time) for religious reasons, because of busy schedules or for extreme dieting. Short-term fasting could mean skipping a meal, whereas long-term fasting could last several days or weeks.

In the case of extreme dieting, people may head to the grocery store and, in their state of self-imposed hunger, buy a lot of food that would undo the results of the recent dieting.

"Fasting has been shown to increase brain reactivity to particular types of food over others," the researchers wrote.

For this study, the researchers conducted a two-part experiment, one in a lab with 68 paid participants and the other in a local grocery store with 82 participants.

In the lab experiment, the participants ranged from 18 to 62 years of age and 71 percent were women. The participants were told not to eat any food for five hours before coming to the lab. The 68 participants were placed in groups of six to 12 and staggered between 12:00 pm and 5:00 pm over the course of two weeks.

When they arrived at the lab, half of the participants were given a plate of crackers and told to eat until they were no longer full and the other half were given no food.

Each participant was then asked to shop in a simulated online grocery store. The grocery store offered a mix of low-calorie foods, such as fruits, vegetables and chicken breasts, and high-calorie foods, such as candy, salty snacks and red meat.

No food prices were displayed on the website. 

The results of the experiment showed that people in the hungry group purchased 14 items, eight of which were low-calorie foods and six of which were high-calorie foods.

On average, the people in the full group purchased 12 items, eight of which were low-calorie foods and four of which were high-calorie foods.

Overall, the hungry participants purchased two extra high-calorie food options compared to the full participants.

Results of a previous study suggested that grocery shoppers were most likely to be full between 1:00 pm and 4:00 pm and hungry between 4:00 pm and 7:00 pm.

At the grocery store experiment, the researchers recorded the grocery store selections of the participants as either high-calorie or low-calorie and then noted the time of day.

The results of the experiment showed that people purchased an average of 11 low-calorie and four high-calorie food options between 1:00 pm and 4:00 pm.

Participants purchased an average of eight low-calorie and four high-calorie food options between 4:00 pm and 7:00 pm.

While people who shopped later in the day did not purchase more high-calorie or low-calorie food options than those who shopped earlier, people in the earlier group purchased three more low-calorie food options compared to the later group.

"Even short-term food deprivation can lead to a shift in choices such that people choose less low-calorie, and relatively more high-calorie, food options," the study authors wrote.

In an Editor’s Note in JAMA Internal Medicine, Rita F. Redberg, MD, MSc, added commentary on this study.

"I think all diet guides include the advice to 'never go grocery shopping when you are hungry'—and when I had young children, I added 'and never with young children'—because either of these factors seem to lead to less wise food choices," Dr. Redberg wrote.

"Tal and Wansink offer scientific support for this common sense advice in their study of grocery store purchases after short-term fasts," she wrote.

This study was published in June in JAMA Internal Medicine.

No outside funding was used for this research. No conflicts of interests were reported.

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Review Date: 
June 23, 2013