It was a controversial move when a health insurer began requiring people who were obese to literally pay the price of not doing anything about their weight – but it worked, a new study finds.

When people had to choose between paying up to 20 percent more for health insurance or exercising more, the majority of enrollees met fitness goals one step at a time via an Internet-tracked walking program, according to a joint study by the University of Michigan Health System and Stanford University.