Schools have begun ditching soda machines en masse, according to new research from the Robert Wood Johnson Foundation. Here's what their researcher Yvonne Terry-McElrath found when she looked at how many secondary schools stock soda drinks:

"We've seen work on this issue from a lot of different groups," Terry-McElrath told me in an interview. "You have policymakers at the state level, and also more local, moving policies into this direction. I also think you're seeing movement from parents and individuals who are becoming more aware of what is and isn't healthy."

The big question, however, is whether this will have an impact on calorie consumption. Schools are not, after all, the only place where students have access to soda. Students can grab a soft drink from a nearby corner store or at home.

One statewide study in California - where schools banned sodas and implemented new nutritional criteria for cafeterias - found students to consume 158 fewer calories daily, even factoring in everything they ate elsewhere. But a separate study of 20,000 students - followed from kindergarten up through eighth grade - found no correlation between obesity rates and access to soda vending machines at school.

"The research is pretty mixed" says Terry-McElrath. "We've got several papers looking into that, but at this point. I know what we'd like to see, but at this point, we just don't know."