In the effort to make workers healthier, employers and insurers have dangled carrots. They've threatened with sticks. Now, they are trying games.

A growing number of workplace programs are borrowing techniques from digital games in an effort to encourage regular exercise and fosterhealthy eating habits. The idea is that competitive drive -- sparked by online leader boards, peer pressure, digital rewards and real-world prizes -- can get people to improve their overall health.

Geologist Deanna Gerwin enrolled in the game offered by her employer, Coeur d'Alene Mines Corp. in Coeur d'Alene, Idaho. She selected healthy tasks that she was already doing, such as getting eight hours of sleep a night. But when she saw that other employee teams were outstripping hers, she ramped up her efforts to generate more points, such as eating fruits and vegetables five times a day and walking 10,000 steps daily. On weekends, she logged in to do extra health quizzes that padded her point total. Soon she made it into the top 10 in the rankings.

'I was surprised I got so into it,' says Ms. Gerwin, who says she rarely plays traditional digital games such as 'Angry Birds.'

A survey of employers released in March by the consulting firm Towers Watson and the National Business Group on Health found that about 9% expected to use online games in their wellness programs by the end of this year, with another 7% planning to add them in 2013. By the end of next year, 60% said their health initiatives would include online games as well as other types of competitions between business locations or employee groups.

Researchers say using videogame-style techniques to motivate people has grounding in psychological studies and behavioral economics. But, they say, the current data backing the effectiveness of workplace 'gamification' wellness programs is thin, though companies including WellPoint Inc. and ShapeUp Inc. have early evidence of weight loss and other improvements in some tests.

So far, 'there's not a lot of peer-reviewed evidence that it achieves sustained improvements in health behavior and health outcomes,' says Kevin Volpp, director of the University of Pennsylvania's Center for Health Incentives and Behavioral Economics.

Moreover, some employees may feel unwanted pressure from colleague-teammates or bosses when workplace competitions become heated, though participation is typically voluntary.

Some companies say they are seeing enthusiasm. A Samsung Electronics Co. semiconductor plant in Austin, Texas, offered a weeklong walking contest in the fall using a program from insurer UnitedHealth Group Inc. that lets employees form teams and track their results. The company will probably use it again for a planned Olympics-style matchup, which will involve events such as relay races wearing clean-room suits, said Charmaine Winters, seniormanager of human resources.

Employers often award prizes and financial incentives to winners of the games, which typically also have digital rewards like badges. Game companies say they've seen prizes as big as cars, as well as extra days off, preferential parking spaces and cash, but often employers offer health-savings-account contributions.

A growing number of companies are trying to grab their business, including ShapeUp, Virgin Group's Virgin HealthMiles, RallyOn Inc., RedBrick Health Corp. and Keas Inc., which provides the Coeur d'Alene Mines game.

Big insurers are also getting in the game. WellPoint, which already offers a wellness incentive program, is planning a new feature that lets workers track their steps using a pedometer device and compete for digital badges and rewards. Aetna Inc. has a 'Get Active!' initiative that lets workers form teams aimed at fitness and healthy-eating goals. Its members can access a digital game called Mindbloom that lets them create a tree that adds leaves as they perform tasks like drinking water.

Joseph Hodges, chief executive of Inetico Inc., a Tampa, Fla.-based health-costs management company, offers health insurance-premium discounts to employees for advancing through the levels of HumanaVitality, a game from Humana Inc. that takes players from 'blue' to 'platinum' status as they do wellness tasks. Partly because the financial value is significant, he says, he likes that the game requires participants to back up fitness claims, typically with digital devices such as pedometers and heart-rate monitors.

Monsanto Co., which used the ShapeUp platform to run several team contests, decided to keep prizes small and let employees vouch for themselves. 'The more you make it formal, the more burdensome it might feel,' says Carolyn Plummer, a health and welfare benefits leader who said she was afraid employees would feel they were 'being watched' if tracking devices were used.

Some researchers say workplace programs could create a backlash among workers who feel coerced to participate, either because of strong financial incentives or pressure from bosses and peers. 'It could be a bit of a feeling like, 'they're manipulating me,'' says Debra Lieberman, director of the Health Games Research national program at the University of California, Santa Barbara. 'There could be tensions between colleagues.'

After Sunrise Senior Living Inc. launched an online weight-loss contest using RedBrick in January, the executivedirector and some workers at its Stamford, Conn., location got deeply involved in their team. The director, Amy Silva, says that once when she was poised to buy a soda, an employee suggested water instead. The regular staff gathering switched to a veggie spread instead of junk food, sparking some grumbling from non-dieters. Some team members started walking at lunch and wearing special pins with motivational slogans. After they came in with a high ranking, they placed a team picture and trophy in the facility's foyer.

'My team is very competitive, and so am I,' says Ms. Silva, who says she lost around 40 pounds.

At AOL Inc., a walking contest that used Virgin HealthMiles in the summer drew in some participants who initially used a message board to voice worries that certain team members were dragging down results by not taking enough steps, says Leah Myers, a specialist in the company's human resources department. Ms. Myers says the company purged those messages, and employees' concerns eased once they were told many prizes including the biggest one -- a three-day hotel stay -- were tied to individual scores.