Walt Disney Co. will reportedly stop accepting some junk-food ads on TV programs, radio shows and websites aimed at children. Disney Chief Executive Bob Iger and first lady Michelle Obama plan to make an announcement today in Washington, sources say. The United States faces an obesity epidemic. Nearly one-third of U.S. children are overweight or obese, and a 2006 Institute of Medicine report said junk food marketing contributed to childhood obesity. The Disney move follows New York Mayor Michael Bloomberg’s announcement last week of a plan to ban sugary drinks larger than 16 ounces in most restaurants, theaters, delis and vending carts throughout the city.