Ninth graders attending a school that’s within a block of a fast-food outlet are more likely to be obese than those whose schools are a quarter of a mile or more away, according to new research from economists at the University of California and Columbia University. The study, which looked at millions of students over the course of nearly a decade, was detailed enough to allow researchers to observe childrens’ obesity rates before and after a new fast food outlet opened nearby. Obesity rates were five per cent higher among ninth graders whose schools were within one-tenth of a mile of a fast food restaurant, they found. “I think we got as close to proving causation as any other study has, and probably as close as is feasible with the existing data,” economist Enrico Moretti, one of the paper’s authors, told the New York Times. Meanwhile, the National Restaurant Association dismissed the study as flawed, as it didn’t take variables like exercise into account.