I think you're understating "not completely free market" a little more than you might realize.  Calorie prices are overwhelmingly distorted by what the government chooses to subsidize.  I don't know what RFK Jr's plans are; but, if I were in charge of tackling the obesity epidemic, one of the first things I would look at doing is aggressively phasing out the massive corn subsidies - thus, taking the govt thumb off the scale in favor of all the unhealthy corn by-products.