Several counties on the list also appear on the list of wealthiest US counties ~ and, not coincidentally, the most expensive areas to live. (Marin, CA, number one on the list, is extremely affluent, as are San Mateo CA, Fairfax VA (Washington DC's toniest suburbs), Sarasota FL, etc.)

Maybe folks paying mortgages and property taxes in these areas are too broke to overeat ~ ?

Conspicuously absent from the skinny list: the US counties with the second- and third- highest per-capita incomes in the nation, Somerset and Middlesex in New Jersey. Also in the metro New York area is Westchester County, NY, once the very wealthiest among US counties and still in the top five or at least ten ~ not skinny there, either.

In Orleans Parish, Louisiana (we call'em parishes instead of counties in our unique and crazy little state), we're mostly pretty fat. The food is too good, and the weather is too damn hot and steamy to exercise much most of the year.