The USDA publication "Amber Waves" recently released a report well worth reading titled, "Fuel for Food: Energy Use in the U.S. Food System" ~ Population growth, higher per capita food expenditures, and greater reliance on energy-using technologies boosted food-related energy consumption in 1997 to 2002 ~ by Patrick Canning. Based upon the release, the NYT's wrote this article: Math Lessons for Locavores.
In a nutshell...
...while total per capita U.S. energy consumption fell by 1 percent between 2002 and 2007, food-related per capita energy use grew nearly 8 percent as the food industry relied on more energy-intensive technologies to produce more food per capita for more people.
It goes on to describe where the biggest growth was:
To accommodate the foodservice industry’s growing demand for processing services, the food manufacturing industry added only 4,800 new food preparation jobs but substantially increased energy consumption. Between 1997 and 2002, food processors’ energy use (direct and embodied) grew 49 percent, a larger increase than any other segment of the food system. This increase amounted to 2.7 million Btu per person, or roughly the heat energy equivalent of an additional 24 gallons of gasoline per person annually. As a result, the food processing industry surpassed the wholesale/retail industry, moving into second place behind households as the largest user of energy in the food system.
Buying a larger percentage of prepared foods and eating out or drinking coffee out has increased energy use.
Although the food service industry outsourced much of its food preparation services between 1997 and 2002, industry energy use increased 47 percent—the heat energy equivalent of roughly 16 gallons of gasoline per person. The proliferation of coffee shops and eating places—with buildings to construct or renovate, equipment to manufacture, new kitchens to run, and buildings to light, heat, and cool—has added to energy use by the food system. In 2002, 479,000 food and beverage service establishments operated in the United States, up 7 percent from 1997. By 2008, this number increased to 546,000.
Because the years which were studied were before the financial crisis, I'd expect some changes related to less affluence of Americans.
The ERS energy flow analysis looked at three distinct points in time (1997, 2002, and 2007); the results cannot be used to determine a pattern or trend in food-related energy use. Many factors can and will affect energy use by the food system. Adjustments in how Americans spend their food dollars, for example, could reduce future food-related energy use.
I agree with their conclusion based upon the high level of unemployment and the drastic shift in economic conditions since the time of the study. One trend, however, is that American's are more and more used to eating prepared foods and the efficiencies of producing those convenience foods have made them reasonably priced. If we see packaging, transportation, and refrigeration costs increase these conveniences will become less affordable. Economic conditions are and may continue to affect the number of persons patronizing eating and coffee establishments, and owning mega-kitchens with second refrigerators, too.