You are here

Fattening Fasting: Hungry Grocery Shoppers Buy More Calories, Not More Food

Tal, Aner and Brian Wansink (2013). Fattening Fasting: Hungry Grocery Shoppers Buy More Calories, Not More Food. JAMA International Journal of Medicine, 173(12), 1146-1148. doi:10.1001/jamainternmed.2013.650.

The amount of food purchased and consumed after fasting has been shown to increase.  But fair scrutiny hasn’t been paid to the healthfulness of items purchased after a period of fasting. Fasting increases brain reactivity towards particular types of foods, so in conducting this study we wanted to see whether people would also choose more high-calorie options, relative to low-calorie options, after short periods of deprivation, such as skipping a meal. 

A laboratory study was conducted with 68 participants on two days, from noon to 5:00 pm each day.   Participants were asked to fast for 5 hours before hand.  They were separated into groups of 6 to 12 individuals.  Two conditions were established wherein half of the groups were given a plate of crackers and asked to eat a sufficient amount to feel satiated and the other half were given no food.  All participants were asked to shop in a mock online grocery store that provided a mix of low-and high-calorie items with no given prices.  Every high-calorie food had a corresponding low-calorie alternative.  

Participants who did not eat prior to mock online shopping chose a greater number of high-calorie foods. There was no difference in the amount of low-calorie options selected between conditions.   

In a follow-up field study, the purchases of 82 participants were tracked at different times of day: 1:00-4:00PM to represent when participants were most likely to be full and 4:00-7:00pm to represent when participants were most likely to be hungry.  Purchases were categorized as either high-or low-calorie and then researchers calculated the ratio of high-to low-calorie items. Those who shopped during the higher hunger hours chose less low-calorie items than participants making purchases at the lower hunger hours. 

The results of these studies show that even short-term food deprivation can lead to unhealthy food choices relative to low calorie options.  We suggest that consumers should be mindful of their hunger level and make decisions about food when sated.