I just shop for one person, and after 3 weeks of eating healthy, cooking more, and not eating fast food every night, I noticed a HUGE change in my shopping cart at the grocery store. I tend to stop every day because I'm pretty random in what I want from day-to-day. So I don't buy much. But here's an example from recently (now), and before (then).
Now
Produce (orange, watermelon, green pepper, red pepper, pre-chopped onion, fresh cilantro herbs)
2% milk
Egg beaters
2% pepper jack cheese slices
Low fat sour cream
Salsa
Fat free tortilla shells
2-3 Healthy Choice dinners
Bag of frozen peas and carrots mix
1 lb of chicken breast
Low-sugar oatmeal
Yoplait Whips! yogurt
Pack of Fruit2O
Then
2-3 frozen meals (sometimes Healthy Choice, sometimes not)
12-pack of diet coke
Chips Ahoy cookies
Pringles chip
Cheddar cheese, pre-sliced
Peanuts
Donuts for breakfast
(And most meals eaten at McD's, Sonic's, BK, etc.)