Have big-box superstores helped to make us fat?

A woman pushes a cart at a Costco store in Hackensack, N.J., in 2013. Big-box stores are effective delivery devices for fattening foods, economists argue in a new study.
A woman pushes a cart at a Costco store in Hackensack, N.J., in 2013. Big-box stores are effective delivery devices for fattening foods, economists argue in a new study.