[lenzm]

> I'm very confused how that has to do with anything?

Presumably people in the country are more easily able to grow vegetables. If they aren't doing it, then it implies that growing vegetables isn't worth the time.

I think there are other confounding factors like income and education.

[ozim]

I would say one confounding factor is city people can get by on a salad an quinoa. If you live and work in country side beans, potatoes, meat are must have in a diet.