“The [laws] have evolved with the implementation of the Affordable Care Act," Jennifer Patel, director of wellness engagement at Hallmark Business Connections, said. "Employers and organizations find themselves in court, [with employees] questioning, ‘Is it legal for employers to ask me to submit to these biometric screenings or health risk tests?’”

Whether or not the lawsuits succeed, even the hassle of dealing with litigation is a major turnoff for companies.

And of course, litigation is a symptom of a potentially greater problem that firms want to avoid: Angry employees.

Some workers respond poorly to health and lifestyle lectures from their employers, a negative effect that might have a greater impact on a company's bottomline than whatever savings are achieved through a wellness program.

One prominent expert, Al Lewis, a former Harvard economist and CEO of Quizzify, asserts that corporate wellness programs are almost always a waste of money.

Virtually no corporate program, he argues, has been proven to substantially reduce the weight of its employees in the long term. Lewis furthermore describes many programs as "weight-shaming," which not only demoralizes overweight workers but can push them into unhealthy behavior, such as crash diets.

LuAnn Heinen, vice president of the National Business Group on Health in Washington, suggested that the future focus of wellness programs will have to include other goals besides improving employees' physical health.

“The evidence is becoming clearer that physical health is not the main driver of productivity, performance, and business outcomes,” she said.