The world's food reserves are at their lowest. The U.S.A. has only three weeks worth of food stocked away.
How much food do you need? You can't really know that until you know what you're planning for. A three day local power blackout is easier to survive than a nuclear holocaust and worldwide collapse of the modern world.
Many people are willing and able to buy 72 hour kits to cope with short term emergencies. The images of Hurricane Katrina and still strong in people's minds and nobody wants to go through what some residents of New Orleans suffered because of their lack of planning and resources (most people drove out of the city before the storm).
You can buy reserves of food for a family of four for a year, and that's great. But if, after that year is over, the US dollar will no longer purchase foods from across the world, or pay for the energy needed to transport them here, or the only government is a local warlord/gangster. Or if nuclear fallout or a pandemic virus is still active -- you need to relearn how to farm.
If you live in a suburban area, you can try relearning to hunt. In many areas in the United States there's more wild life than there was fifty years ago. Here in St Louis county I've seen a pack of ten to fifteen raccoons eating garbage on a city street late at night. Oppossums run across the road in front of me more often than cats. Deer devouring lawns and gardens are a big problem in Des Peres, and I've seen them dash across the street in front of me -- fortunately not hitting me. Rabbits and squirrels are also common.
However, if a catastrophe happens, many people would go out and hunt these animals and so their supply would go down rapidly. Hunting cannot sustain a large human population, even when the entire world was a primal wilderness. That's why we switched to agriculture 10,000 years ago.

So one idea is to buy one of the books on identifying, gathering and cooking with wild edible greens. For example, I know that dandelion greens make a good salad, though only when they're young and fresh early in the spring. Many "weeds" are edible and probably taste good as well. And you will certainly find a lot more edible plants if you prowl woods and fields -- even vacant lots and the lawns of abandoned houses -- than wild animals once everybody with a gun starts hunting.
(Come to think of it, I'd stay out of suburban lawns, because so many people have treated them with pesticides. You may eat a large residue of poison.)
You can't really have too much food stored away. It's a form of insurance -- better to have it and never need it than to need it and not have it or not have enough.
So while freeze dried food stored away in #10 steel cans that comes in prepared delicious entrees that are ready to eat as soon as you add hot water is great, it's not a long term solution. So many people store red wheat berries away in 5 gallon buckets. Keep in mind that you'll also have to grind it into flour and then bake the bread.
You can buy canned food. It won't go bad, but will lose its taste, texture and nutritional value. You can simply keep a large supply on hand and rotate it. Put the new cans in the back and cook with the cans in front which are the oldest (but not so old the food tastes bad).
Nonfat dried milk powder is also a common disaster food stored away. You must keep it dry and away from the air.
Be prepared -- that's what the Boy Scouts taught me. You may not believe that we're ever going to face a huge food shortage -- and I hope you're right -- but nobody can deny that natural catastrophes can happen to us all. food for survival is something to learn about and store now, before you need it.
Next: Survival Food Kits -- foods to store for emergencies.