I think the first step that most people can agree on is to remove all agricultural subsidies and tariffs (and ethanol requirements). That way, the things being produced in -- and imported to -- the US more closely match what consumers actually want, without government putting its finger on the scale.

As the costs of subsidized, unhealthy food rise, consumption will decline. This, of course, assumes that the demand is induced by artificially low prices. If people consume just as much high-fructose corn syrup at higher prices, then you have a cultural challenge on your hands.