American workers, get thee to a gym.

This is open-enrollment season for employer health benefits, and employees are increasingly likely to see "wellness" programs that offer discounts to those who participate. And watch for significant disadvantages, such as fewer health insurance choices, for those who don't opt for wellness.

Companies have long used incentives -- small bribes, such as a $25 break on health insurance premiums, for example -- to get workers to take health-risk assessments that help spot looming problems or unhealthful habits such as smoking, alcoholism or overeating.

Now some companies simply won't allow their employees to sign up for health insurance until they take the risk assessments, said Kirby Bosley, Western Division practice leader with benefits firm Watson Wyatt Worldwide in Los Angeles.

If the assessment discovers manageable problems, you may be encouraged to join a fitness or smoking cessation program. Do that and you're likely to get bigger financial incentives -- somewhere in the neighborhood of $100 to $500 annually, she said.

But if you don't, your employer might restrict your health insurance choices to plans that demand higher deductibles and offer fewer services and benefits, which could cost you hundreds of dollars.

"Employers are drawing a line in the sand," Bosley said. "There will be consequences for ignoring your health."

The carrot-and-big-stick approach to wellness programs is among the most prevalent trends this open-enrollment season, experts agreed. However, other trends also suggest that employees will find it costly to ignore their benefit selections this year.

Not only are benefits choices changing -- largely to require more cost-sharing by workers -- some companies are demanding that workers make active choices or get dumped from the plan completely.

In the past, companies commonly allowed workers to re-enroll in their current benefit choices by doing nothing. Now if you do nothing, you may not be covered at all, said Karen Kocher, chief learning officer at insurance giant Cigna.

"There are radical differences in dealing with open enrollment today than in years past when it was simpler," Kocher said. "People need to be smart about the options, their needs and matching up the two to minimize out-of-pocket spending and get the most out of the coverage."

Other trends: