Essentially, the researchers found that if you increase the number of healthier options for people, they're more likely to choose them over the less healthier options. Here's one of the experiments done:
In another study, a tray with fruit and baked goods was placed at two entrances of a building, with a sign reading: "Please help yourself to one item." At one entrance, the researchers placed a tray containing a small selection: two types of fruit and two types of cookies. They put a tray with a larger selection at the other entrance so that passers-by were presented with
six types of fruit (bananas, red and green apples, pears, tangerines and peaches) and six types of baked goods (assorted cookies as well as croissants and banana nut muffins). While 55% of the participants chose fruit over baked goods from the smaller assortment, 76% did so when choosing from the larger
I had blogged a while back that one shopping rule to follow is to have the majority of your food purchases be fruits and vegetables. You can find the blog here: http://losingweightafter45isabitch.blogspot.com/2009/10/new-food-shopping-rule.html.
It only makes sense, if you surround yourself with a great selection of fruits and vegetables, you'll eat mostly fruits and vegetables. If your kitchen is laden with crap, you'll eat mostly crap.
The same thing goes with restaurants. If you go to a restaurant with only one salad on the menu (and its a salad in name only), you're not likely to order a salad. Go to one with a wide selection of salads, and chances are you'll order a salad.