Last month, US Surgeon General Vivek Murthy launched a walking initiative called Step It Up to combat chronic disease in America. On its face, that seems like a good thing, but health advocates charged that it’s yet another health campaign that shifts the focus from what we eat to how we exercise. It’s a message you often hear from the soda industry, not the surgeon general. WBEZ food and health reporter Monica Eng got a call last week from Murthy, who said he wanted to clarify his stance. Eng joins us with what he said.