In fact, not even then, for most thru-hikers it's more about just getting some protein every day and enough calories, then make up for on-trail omissions by various difficult-to-carry foods at restaurants and grocery stores in towns.

I.e., just keeping it simple is a great way to start. If you choose reasonably light & dry foods without too much packaging, you might shoot for something on the order of a pound and a half of food per person per day, assuming you're not a particularly large person or one that has a high metabolism and/or starts out with zero body fat.

In fact, for short trips you might keep it even simpler by going no-cook entirely, or just make a simple alcohol stove for essentially nothing before spending money on another type of stove (and you might well be happy with the alcohol stove). My favorite "easy to make and effective" stove is the Andrew Skurka Fancy Feast stove.

The main things I eat on backpacking trips are trail bars, jerky, dried fruit, gorp, some sort of bread item with peanut butter, and some sort of "just add hot water" meal for dinner. It doesn't have to be complicated, and the "just add hot water" meal can be a variety of things that are easy to find in your local grocery store (cheaper and easier to get than the dehydrated meals sold in sporting goods stores).

Ultimately you have to decide what sort of food you want (or are willing) to eat outdoors, running the gamut from dead simple all the way to backcountry gormet. I personally like the KISS principle here, but as with so many aspects of backpacking, a person has to figure out their own individual priorities and style.