WHEN are you asking about? This is an incredibly broad question that changes very significantly with the time period you are asking about.
WW2 Leningrad is a very different answer than 1422 Constantinople.
Please clarify.
Are you looking for a specific answer? The levels of agricultural ability, output, methods of obtaining foodstuffs, and the abilities of preservation depend entirely upon which time period we speak. For example, the prehistoric methods of obtaining food and preserving it were radically different from that of the feudalistic orders, and that system is radically different from the methods employed during times of revolutionary upheaval in certain countries.
I'll be able to answer adequately for a time period spanning through either the Roman Empire, medieval Europe, or 20th century Russia, if that's of any help.
For a more specific follow up, what would the answer to this question be if we were discussing, say, 1200 CE?