Carrot or Stick?

Lately, there here have been reports in the news of employers offering cash incentives for their employees to lose weight.  

Employees Earn Cash For Exercising More - WSJ

Obesity is an American epidemic  - in recent studies, it was found that 66% of Americans (over the age of 20) are overweight, with approximately 34% of adults (roughly 72 million people) are estimated to be obese.  Of the younger population, 9 million are classified as overweight or obese.  It has been forecast that by the year 2015 nearly 1 out of every 4 children will be overweight.  

The statistics regarding obesity related illnesses and consequently deaths are equally staggering.  Putting aside the fact that almost 80% of deaths attributed to cardiovascular disease and cancer could have been prevented by living a healthy lifestyle, the monetary cost of physical inactivity and poor eating habits is astounding: in 2005 the costs attributed to cardiovascular disease reached $393 billion dollars in the United States alone.

So with this in mind, I wonder if earning a few extra bucks is actually incentive enough to get people to make a change when the clear and evident health risks of being unfit are apparently not stimulus enough?  

Will the carrot be more of a catalyst for change than the stick?  Would people be more apt to adopt a healthier lifestyle for a cash reward, or would they be more likely to give it a whirl if they knew that they'd have to pay a fee instead?

I know that personally, I'm more likely to respond to the stick.  What about you?

NHANES

CDC