Common sense suggests that sprawling out on the sofa and binge-watching "The Walking Dead" while plowing through endless bags of potato chips and super-sized, sugar-laden sodas has got to be less healthy than, say, knocking off a couple of miles on a treadmill. For administrators of corporate wellness programs, however, proving the link between good health and lower corporate medical bills has proved, well, elusive.

Which is a problem, because according to a report published last year by the RAND Corp. – "The Workplace Wellness Programs Study" – slightly more than half of U.S. companies with more than 50 employees offer workers some sort of wellness program. And while most of these companies were certain that their wellness plans "reduced medical costs, absenteeism, and health-related productivity losses," only about half the organizations had ever formally evaluated their wellness plans. Of those that had, only 2 percent reported actual cost savings.

Return on investment, of course, is what gets obsessed over both to justify and to reject implementation of corporate wellness programs. Citing a number of peer-reviewed studies, the Society for Human Resource Management found that wellness programs returned an ROI ranging from 3.27:1 to 6:1 over a three- to five-year period.