As much as I wish this would happen, along with forced daily exercise routines, its not likely.  What is more likely is a soft nudge approach, like the kind that was adopted with the cigarette industry and then with public smoking.  Sue the food manufacturers possibly.  Adjust insurance rates to overcharge for obesity.  Make public transportation somewhat inaccessible to the ginormous.  Do the same with seating in public places, restaurants, buses, etc.