Last time I did it, I came back after a week a bit hungry, rather dirty, and feeling fine. The Appalachians in late spring are a lovely place for a survival hike. That was 1978, IIRC; I've picked up more savvy since then, but no longer have the Metabolism From Hell that would let me be comfortable in a blizzard wearing nothing but a rain-shell and boots.
Which brings up the point that "survive" specifies neither "where" or "with what." Someone else answered this that, dropped naked at the North Pole on New Year's Day, he'd last about an hour; let him grab his bivvy-bag and drop him in any temperate climate, and you can come back for him in a year and he'll have made something to sell to you. The most basic tools are a knife and a fire-lighter and a blanket; one of my old hiking buddies (Anybody know if Gene Prater is still out there hiking?) survived a long weekend stranded on the Alaskan North Slope with nothing more.