One group would be rewarded $1.40 for every day they met the goal. Members of the second group got to partake in a daily lottery with similarly-priced prizes for every day they succeeded. But the third group was presented with a lump sum of money at the beginning and saw that sum diminish by $1.40 every day they failed to hit the steps target.

Those in the group given a chance of making money every day only hit the steps target 35 percent of the time. The lottery group similarly hit the target 36 percent of the time.

But the group faced with losing money achieved the goal 45 percent of the time.

"Financial incentives framed as a loss were most effective for achieving physical activity goals," concluded the report, authored by Dr. Mitesh S. Patel of the University of Pennsylvania Perelman School of Medicine.

The conclusion of the study raises some uncomfortable questions about the extent to which employers can or should go to promote a healthy workforce.

"I am not sure this means that threat of punishment is a good long-term motivation strategy, as it might also lead to demotivation," Dr. Hanneke den Ouden, at the Donders Institute for Brain Cognition and Behavior the Netherlands, told MedPage Today.

Critics of wellness programs levy a number of criticisms of such incentives, including that the shame and distress they may cause employees may outweigh whatever benefit they yield in terms of weight loss.

In addition, some experts point out that the emphasis on exercise is misguided, since most research has concluded that diet plays a much greater role in determining weight than physical activity.

Still others suggest that some businesses that set up such incentive programs, particularly if they are tied to insurance premiums, do not do so with the goal of producing healthier employees, but simply to charge employees more for their health insurance. By setting weight loss goals that many employees will inevitably fail, companies can justify shifting more of the cost of health care to workers.