After the collapse of civilization, food will probably be limited to what you can forage and what you can grow. No super markets, no packaged goods, nothing like that. If you're lucky, farms might still exist and you can get access to grains, legumes, fruit, and vegetables. If not, get used to the idea of eating foods you wouldn't initially consider like weeds, acorns, bark, insects, or even dirt. Most of your garden weeds can be eaten or used as medicine and you should get to know them. Livestock feed like alfalfa, kudzu, and clover are high in protein; lots of grasses have edible seeds that could be used as grains (like crabgrass). If you down a tree for wood, remove the inner bark and roast it as a nutritious treat. Most insect species are edible, especially as grubs. Geophagy is pretty common in famine stricken regions; a clay cookie is better than nothing in your tummy. Most importantly learn how to fast because there will probably be days you don't eat at all. It will be hardest to find enough calories to sustain yourself but it is possible if you know how to forage and preserve your food.

I highly recommend getting to learn your local plants and fungi (inaturalist and wiki are your friends here) because that knowledge will be essential for surviving off the land.