Michelle Obama is to back plans by the world’s biggest retailer, Walmart, to provide its customers with healthier and more affordable food options as part of a drive to cut US obesity levels. The United States’ First Lady has made promoting healthy eating her key initiative in the White House. She will join Walmart representatives at a press conference to launch the initiative later today. Walmart is planning to cut prices on thousands of its packaged foods, reduce fat and salt content, and cut the prices of fresh fruit and vegetables. By 2015, the company hopes to have lowered salt content by a quarter as well as slash sugar levels in foods.