First lady Michelle Obama will unveil Friday the country's first update to nutrition labels in more than two decades — a move that helps cement her campaign to encourage Americans to eat healthier. The new Nutrition Facts labels, which will take effect in two years and appear on billions of food packages, for the first time require food companies to list how much sugar they add to their products and suggest a limit for how much added sugar people should consume — two changes vehemently opposed by many food companies. The impact of the rule is difficult to overstate —...