Are you wanting a serious answer?
Economics play a big part in nutrition obviously. The northern states and even the western ones, even when figuring in their higher cost of living, tend to make more than the Southern ones-the conservative states. Thus, they can afford to spend more on higher quality of food, rather than just worrying about quantity.
There is a cultural factor. There are more minorities living in the South-Hispanics and Blacks. Traditionally, both of these cultures tend gravitate more towards food-they eat richer, higher calories more often than Caucasians or Asians. The Southern Hospitality is very concerned with the quantity of food-where we host true BBQs on the weekends. Really, nobody needs to eat that much meat. The
The biggest factor is poverty. Blacks and Hispanics tend to be poorer than Caucasians. Poverty v. Obesity shows a positive correlation-higher stress, poor lifestyle choices, low motivation, lower education, lower income, more children, lower standards of living.
Most people are genetically designed to become fat eventually. Some keep this in check with exercise. Poorer people are less likely to go exercise in gyms or public parks-due to lack of them in their areas.
Also Northerners get snow-it takes substantial number of calories to keep you warm. In the South, while you would think the heat would melt away the calories-but no, we stay inside with our A/Cs.
We see you walking everywhere. Nobody really walks down here in the South, as evidenced by our lack of pedestrian sidewalks. People in cars (rather their SUVs and Monster Trucks) throw cigarette butts at you while yelling obscenities.
God forbid someone ride their bicycle. You are just asking to be run over.