USDA economists have just produced a theoretical study proposing – surprise! – that knowledge of nutrition is not sufficient to change dietary behavior. What they call “immediate visceral factors” (i.e. hunger, food in front of you, large portions) overpower “cognitive dietary information.” They don’t put it this way, but that’s why personal responsibility doesn’t work. You have to change the food environment to make it easier to make better choices. It’s nice to have some evidence….