If you've ever grocery shopped when you were hungry, you know the pitfalls of that adventure: You're more likely to leave the store loaded down with food you don't want—or need—but crave and can't resist because you're so hungry. The answer to that problem: Don't grocery shop hungry. Grab a small snack before you hit the aisles.

Now researchers have discovered exactly what type of snack you need if you're interested in making healthier choices once you're in the store. A study from Cornell University's Food and Brand Lab found that people who eat a healthy snack, such as an apple, before shopping buy more fresh produce than people who eat a cookie or no snack at all.

The same finding was true for people who shopped online: People who ate an apple before conducting virtual grocery shopping selected more fruits and vegetables than people who ate a cookie or no snack at all before surfing the online grocery.

"You can influence your cart with something as simple as what type of snack you have before you go into the store," says Kate Geagan, RD, author of Go Lean, Get Green: Trim Your Waistline with the Ultimate Low-Carbon Footprint Diet. "Eating that candy bar in your car before you run into the store may have a double whammy. It could sabotage you in ways that you're not really thinking about."

Once you're actually in the store, another trick may help keep you on track: a grocery list. According to a new study, shoppers who use a grocery list have a lower body mass index (BMI) than people who shop without one. Of note: This study was conducted in low-income, urban neighborhoods, and the shoppers were overweight or obese at the time of the study. Still, the individuals who had a grocery list and stuck to it were more likely to have a lower BMI than those without one.

Both of these findings, while small, have the potential to create real, lasting impact on your health in the future. "What your mind-set is when you walk in, even the subtle psychology you might not be aware of, is really helpful and powerful," Geagan says.

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