I too am from a very rural community in Wisconsin. Most of my extended family still live there. The obese from what I can tell are obese for the same reasons suburban and urban dwellers are: sedentary lifestyle, dietary choices, and non-modifiable factors like genetics. There is possibly a higher consumption rate of fresh corn on the cob during the summer (with butter and salt of course) because so many farmers and gardeners grow it...and because it's delectable. . But otherwise, the grocery stores carry the same things any other grocery store carries. Five miles south of my childhood home is a local frachise grocery store, and 20 miles north is a Wal Mart Supercenter. Fresh produce is very abundant in the summer! You can't drive more than a couple miles without seeing handmade signs for fresh berries, tomatoes, or corn. There are lots of commercial berry patches, Amish wives selling surplus, etc.
My parents receive medical care at a Mayo Clinic affiliated practice; my mom's MD even does dietary education with her, as she has high triglycerides and is trying to avoid meds. Local EMS is all volunteer, and the nearest hospital is 20 miles away, but anecdotally I see more people dying not because they didn't get EKGs but because they don't call 911. Men especially -- the Scandinavian farming type tend to be quite stoic. But my 93 yr old grandma survived bilateral PEs a few years ago, her family and team was so quick to act!
Excercise is an issue in the winter. It's often dangerously cold to go for a walk, and daylight is short. At winter solstice time, the sun sets before 1630. They've had some small fitness centers open in recent years though, and people can buy a treadmill as easily as suburbanites can -- nearest Wal Mart is 20 miles. My parents took up Nordic skiing and snow shoeing for variety, weather permitting. :)