If you’re looking to lose or maintain weight, you might think of shopping when your belly’s full. That’s the upshot of a new paper looking at how people shop when they haven’t eaten. Simply put: If you skip a meal, you’re more likely to buy high-calorie food, and probably eat it later on.
Aner Tal and Brian Wansink, researchers at Cornell’s Food and Brand Lab, conducted two experiments. In the first, 68 participants were told not to eat for five hours before coming to the lab in the afternoon. Then one group got to eat until they were “satiated” (they only got Wheat Thins, but still), while the other group got nothing at all. When the groups were subsequently asked to shop in a simulated market, the second group bought 18.6% more food, including 31% more high-calorie stuff.
In the second experiment, the researchers went to an actual market and observed purchases both right after lunch (when shoppers are less likely to be hungry) and in the late afternoon (when they’re getting peckish again). They looked at the ratio of high- to low-calorie foods in people’s baskets, finding that the later shoppers had 26.7% fewer low-cal items.
Tal says if they had counted calories (instead of products), the satiated/non-satiated and post-lunch/late afternoon differences might have been even bigger. The research also didn’t look at consumption–though Tal says previous work shows availability has a strong bearing on eating decisions. If you buy unhealthy, you’re more likely to eat unhealthy.
He says the weight-conscious “might want to eat something before shopping” and even before making a list. Moreover, it could pay to go to the store with a clear head. Studies show that “a lack of cognitive resources can increase impulse purchases and hedonic choices,” Tal adds.