May 6/New York/ABC News -- Researchers at Cornell University have examined shopping while hungry. Not only does filling up a food cart while on an empty stomach lead to out of control snacking in the short term, it may condemn the shopper to an entire week's worth of unhealthy eating.

The Cornell researchers followed 68 shoppers as they clicked through an online grocery site that offered a mix of healthy choices -- including fruits, vegetables and lean meats -- and unhealthy, high calorie snack foods like candy, chips and soda.

The shoppers who did not eat for four to five hours before filling their virtual food baskets bought the same number of items as the shoppers who snacked on crackers before clicking away. However, the hungry shoppers selected more processed junk foods, 23% more on average. A follow-up field test where researchers secretly followed shoppers who had not eaten for several hours found much the same.

"You don't buy more, but you do buy more of the wrong type of calories," noted Brian Wansink, one of the study's lead investigators and author of the new book, Slim By Design. "You buy things like cereal, snacks, chips, candy and other convenience foods that require no preparation and that you can eat right away."

Previous research demonstrated that fasting for up to 18 hours can drive shoppers to make less diet-friendly choices and spend more cash overall. However, this is the first study to show shoppers do not have to be terribly hungry for their judgment to be affected.

Even just a few hours without eating is enough to send a shopper in search of a quick fix to satisfy hunger. Further, as Wansink noted, this is often the state shoppers find themselves in as they rush to the market after a long day of work.

Unfortunately, the effect goes well beyond buying a candy bar for the drive home, Wansink said. Shoppers who impulsively purchase ready-to-eat, low nutrition foods set themselves up for repeated diet disasters because they fill their pantries with junk instead of healthier fare.

"It ends up cursing the rest of your week because you bought way too much of the convenience foods and not enough of the good stuff. So now there is less healthy food for you to choose from at home."

Americans seem to be snacking more than ever. On average, Americans enjoy 2.3 snacks per day according to the latest poll by the Hartman Group. Nearly 30% of people said they snack impulsively while another 17% reach for a snack when they don't feel like cooking. Almost 60% of respondents said choosing a healthy snack is important to them, yet the two most popular snacks choices are chips and soda.