I find that fresh produce often spoils before I can get to it, so I shop about every 2-3 days and only pick up what I need for the next couple days. That said, I don’t cook from cans and boxes – 90% of the time, I shop the perimeter of the store and only venture into the aisles for cleaning supplies and paper products.
On days off, I will cook ahead for several days, so I make a lot of soups and stews and keep things like crackers on hand, so that’s always just a quick heat up. And, unless it has potatoes in it, you can freeze portions so you don’t have to eat the same thing multiple meals in a row. (I have a three-meals-in-a-row limit on leftovers.) You can also plan ahead for lunches and make 5 sandwiches on Sunday night, for example. The reason singles eat out a lot is more about convenience, so plan ahead and make things more convenient for yourself.
And then, invest in food preservation supplies (freezer bags, tupperware/snapware). Let’s say I cook something that calls for onions, and I chop up a whole onion, but I only need a small amount and now I’m left with a ton of chopped onions. The remainder goes into a freezer bag, so for subsequent recipes, I can just pull whatever amount I need from the baggie. Peppers freeze well and whole fresh ginger freezes well. Bread also freezes well, so if you can’t get through a whole loaf before it goes bad, freeze half of it. Or, hell, freeze all of it and pull out a couple slices at a time. Make a whole friggin’ batch of lasagna, but Stick all the leftovers in individual serving portions in the freezer. Bam, now you can have homemade, fresh, healthy ingredients, lasagna whenever you want it.
But also, I’ve just learned to cook in smaller portions. Instead of a whole cup of dry rice (say, for dinner for two), I’ll use a half cup and just make less rice. One rule of thumb I use a lot is that it’s easier to deal with cooked leftovers than raw leftovers. So you got a deal on four pieces of chicken but you don’t want that much in one sitting? So, cook all the chicken and now you’ll have a couple pieces for lunch tomorrow or whatever. I use a lot of bags of frozen veggies and use only what portion I want for myself for that one meal, make a one-person portion of rice, and lookit, dinner is half done already.
If you’re the type of person who does not like/eat leftovers, then I suggest about once a week, invite a hungry friend over and clean out your fridge.