As long as we keep this experiment in supersized settlements (aka cities) we will need some form of fuel intensive food delivery system, no doubt expending more energy than yielded in caloric value. This is not impossible so long as the surrounding rural lands feed themselves locally and synergystically as possible manage energy and nutrient flows. This works by returning the function of the local rural settlements as agrarian communities. They would be self sufficient in food production and do basic level food processing such as baking, canning, milling and perhaps even meal preparation as well. At this level, all transportation could be made by pushcart, horse, bike cart or simply carried.
The goal of each community would be to produce a surplus of food to be sent to larger level communities. A single trip every few days would be sufficient or daily parcelized service in combination with a bus or train trip would also work. Enough of these local communities would have to be created to support larger cities. These cities would also supplant their food production with limited rooftop, vacant lot and community garden agricultural production and food processing would be done in that city and consumed as well. Ideally all waste vegatable oil could be transtesterfied into biodiesel to drive the trucks (that would be traveling a few hundred miles at most) while waste food would be composted or tossed into a biogas generator. Ditto for human waste. Compost created in the big city could be used in the city or carted out of town. Ideally more waste would be turned into usable energy (gas or liquid fuels) in larger settlements and compost in smaller ones.
The food system would not involve multi-state or international trade of crops for economic reasons. My apple juice my kids are drinking comes from apples picked in the US, China and New Zealand, processed in New Jersey and trucked across the country to Oregon. We won't continue to do this. Small settlements will send a few gallons of apple juice (if they have any) to larger cities via truck, train, barge or even human-based delivery services. Combined freight trips will improve the efficiency and operating supermarkets in the cities would be more efficient than a number of corner stores.
It's idealistic, I know. On paper it kind of pencils out, especially if the agricultural techniques are low energy, high labor methods such as bio-intensive cultivation and synergystic farming (which utilizes vermicompost, mushroom raising, small animal(rabbits/chicken/fish) production, raised bed cultivation, and intercropping) techniques. Additionally we would ditch most forms of disposable plastic containers for glass and paper. Both require significant initial energy investments but properly reused or recycled within each community, that too would aid significantly.
To read more about what I think would be an idealistic layout for future settlements read
here. This won't help out those of you in desert regions, but other than that it would be a good start.