This post reminds me of the movie Deep Impact. Public didnt know what was going to happen, but all through the beginning, nothing but cans of Ensure around.
IMO It would take a tremendous amount of trouble to cause the food shortages that people imagine. However, many many people think that the human body is designed for 3 squares a day, when in reality, it isnt. The human body is designed for small meals intermittantly (could be once a day, could be a big once a week). I learned that from the Discovery Channel!

Lets take a situation: How many people actually eat 2000 calories a day (raises my own hand)? Many people (and I for a while) looked at 2000 calories and laughed. I began to cut back though and found that with proper exercise and GOOD food, 2000 calories is an abundance. However, many people feel hungry if they havent consumed the 6000 they "need" a day. I am frightened by a fat man with a gun who hasnt had "enough" food killing me for a pound of rice.
Crazy Vern's Advice: In addition to exercise (which naturally "balances" you metabolic engines) try to cut back on frivolous foods. Foods that are not required, but do this slowly. If too fast, humans become "bored" and will revert to their former habits. Once you get to 2K a day, I do this (keep in mind, Ive got problems

): I roll a die every day. Get a six, no eating, just water and multi vitamen. Ive only had it once where I got to 3 days without, but still. If I roll a 3, half rations for the day.
You will not believe how your body will react to that. I feel great, lost alot of weight (despite a now sedentary desk job) and my food budget is 40 bucks a week (saves me money to take my love out to dinner really fancy). Cutting sodas (diet or not) unless a treat literally saved me 10 bucks a week. Thats half a pound of H335 powder!
The point, yes I know: The point is we eat too darn much and in a frequency that is genetically puzzliing to our bodies. They form fat because in the presence of more food, they think famine is coming. Reduce your intake and if the SHTF, you will be prepared and ready while many others languish in "hunger" pains. Also, now is the time to begin learning what is tasty in the woods and what isnt. Learning of tubers, fruits, berries and leaf types (leaves of 3 leave it be, leaves of 4 eat some more!) to supplement an existing potential food source to extend one's food capability. Also, those who have land, begin thinking about farming techniques and food storage, because nuclear winters are the longest of them all...