Thanks for the link. I agree that preparation time is an important consideration. I do think that the food desert criterion (> 1.6km to the nearest supermarket in urban centres) seems very restrictive -- this would make half of most suburbs "food deserts" in the affluent western country where I live.

I find the more recent concept of "food swamps", also explained on that page, to be a (perhaps unwitting) direct challenge to the theory that absence of nearby healthy food is the root cause:

> A related concept is the phenomenon of a food swamp, a recently coined term by researchers who defined it as an area with a disproportionate number of fast food restaurants (and fast food advertising) in comparison to the number of supermarkets in that area.[13] The single supermarket in a low-income area does not, according to researchers Rose and colleagues, necessitate availability nor does it decrease obesity rates and health risks

If this claim is true -- that is, if areas with 1 nearby supermarket have obesity rates no better than areas with 0 -- then it's essentially impossible to blame health outcomes on the availability of healthy food nearby. If an area has nearby supermarkets, it is much harder to make the case that obesity is purely the result of external factors outside a person's control.