For decades, doctors have warned Americans not to overindulge in fast food. So it was striking to see the secretary of the U.S. Department of Health and Human Services sit down to a burger and fries on national television this week. While waiting for a meal at a Florida Steak 'n Shake, Robert F. Kennedy explained to Fox News host Sean Hannity that Americans will be healthier if they start consuming more of what he calls "traditional" ingredients, like beef tallow.