I once joked to my colleague, as he criticized me for being lazy by suggesting taking the elevator from the first to the third floor of our building at Oregon State and thus wasting energy, that it was quite possible that walking up the stairs was less energy efficient. After all, I argued, think of all the energy it takes to provide us with all the calories we need to make it up the stairs: fossil fuels for the farm equipment, transport trucks and electricity for the store; energy to create the fertilizers and pesticides, packaging; plus all of the carbon impacts from these plus methane from livestock, etc. (All good reasons to shop at the local farmer's market perhaps) Factoring in our relative lack of fitness, it seemed like the elevator might be a pretty good deal. I was joking, of course, but it turns out that, according to a couple of people who claim to have done some calculations, I was not too far off the mark.
Now, some caveats: this was mostly about the "typical American diet" which is heavy in processed foods, dairy and meats and comes mostly from supermarkets - nonetheless, it does give one pause. There is one thing that the two researchers did not factor in: that in walking regularly one improves ones health and thus may need much fewer health care interventions throughout life and this may mean a considerable energy savings. It also brings up another conundrum: farmers markets may definitely be the best place to go and get local produce that is in-season and climate appropriate, but what is better, a local hot-house that grows tomatoes in the winter, say, or shipping tomatoes from a hotter climate? (By the way, the obvious rejoinder, that an Oregonian perhaps should not eat tomatoes in the off-season is not particularly helpful - assuming there is a demand, we need to decide how best to deal with it?)