do you really want the government determining what is healthy?

The government's various diet recommendations, from the cardio-toxic "four food groups" to the more recent diabetes pyramids, have merely reflected the shifting corporate hegemony in the agriculture and food industries. There is a tension in the government between those who want to do right by the citizenry and those who want to do the bidding of corporations. I don't think there's an easy answer to your question, because I don't think Americans have made very good choices by "letting the market decide." Because letting the market decide is really just letting the corporate marketeers decide, because those who control marketing control public perception. Supposedly "healthy" yogurt has more sugar than a twinkie and now every can of soft drink has the equivalent of 15 sugar cubes in it. Do we really want to trust "the market?"

Figuring out what is healthy is not rocket science. The healthiest, most long-lived populations on the planet all share one common feature: they all eat a lot of vegetables, with little or no meat or refined sugars. Duh. Eat your vegetables.