Need a financial incentive to lose weight? How does $100, $200, or even $500 sound? Many employers are using “dieting for dollars” programs to encourage workers to slim down. Employees who lose weight are offered rewards, such as gift certificates or reduced health insurance premiums, additional vacation time or–everyone’s favorite–cold hard cash.

It’s like your own personal version of The Biggest Loser: the more weight you lose, the more money you win.

As many as one-third of American companies offer financial incentives, or plan to introduce them, to coax their employees to lose weight, according to the Center for Health Incentives at the University of Pennsylvania. Some employers reward workers for simply completing a health evaluation or enrolling in a class.

Thus far, the programs have had mixed success.  One hospital chain with an overweight workforce paid employees for wearing pedometers and walking as much as they could. The more the employee walked, the more money he received, up to $500 per year. The program was a hit. Half of the chain’s employees signed up for the program and many workers report losing a significant amount of weight.

But other programs haven’t been as successful. A Cornell study looked at seven employer programs and found discouraging results: The average weight loss for employees was just one pound.