That’s a small South. If leaving out Virginia was intentional (!), I have to say it’s severely ahistorical. And our sense of history is supposed to be one of the differences between Southerners and other Americans.
Kentucky, and Maryland, sided solidly with the South in 1860. The real “border states,” with substantial division of sentiment just prior to the secession crisis, were Pennsylvania and Missouri. The former tipped to the North and the latter to the South. (The secession of Maryland, for example, was prevented only by the extrajudicial imprisonment of their legislature; the later partitioning of Virginia was rigged, conducted without the participation of Southern sympathizers from those counties.)
Oklahoma, of course, wasn’t a state, but the Cherokee, Chippewa, Choctaw, Creek and Seminole nations all sided with the Confederacy.
Getting back to the fatness… despite stalwart Southern leadership, the bulging trend is hardly limited to these parts. Washington state and New Mexico might be the most dedicated to the expansion project, by their relative advances in the past 20 years.
A barbecue joint I’m familiar with has a poster: “Memphis. Second Fattest City in America. We won’t stop 'till we’re number one!” But despite Memphites’ best efforts–they are fatter today than when the poster was made–their ranking has actually slipped.