But the critical question for employers, according to Aon, is how do employers push workers across the "behavior change spectrum" from "awareness, to action, to improvement, and finally, to healthy habits"?

Surprisingly, the survey suggests, employers fail to do a couple of key things (among others) in order to get the return on investment they're actively seeking. Both of which are setting employers up for a continued era of unsustainable costs.

One failure is in designing plans without input from employees. While about 50 percent of employers are using input such as focus groups and surveys to gauge attitudes about health, which influences communication strategies, employers aren't doing much else with the response they get from employees.

Only about one in four employers seeks input on incentive and disincentive designs, for instance. Yet, it's been shown that rewards are much more motivational than consequences.

But what kinds of incentives do employees like to see that employers aren't putting into their wellness designs? Maybe a 20 percent reimbursement for a gym membership, or a premium discount for following up with a doctor to discuss a cholesterol problem? 

If employees don't have a sense of ownership and feel invested in wellness, they're likely to ignore the message and employers are likely to get the message wrong, Aon suggests.

This isn't a good start, and it's likely to affect  the other glaring problem employers have with their wellness strategies: a tendency to dismiss accountability even after the employee knows their health risks and status.

Sure, the employee will sign up for the health plan's biometric screening if he or she can get a smaller premium. But their doctor will probably never know what that assessment found, and they'll likely never sign up for those Pilates classes they've been meaning to take.

The survey shows that participation in health risk questionnaires and biometric screenings are the two most popular programs where incentives are offered to participate (84 percent and 64 percent, respectively).

Here's where the statistics get skewed. More than 80 percent of employers provide an incentive to complete a health questionnaire, yet less than 10 percent provide an incentive to address the results of the questionnaire. Additionally, more than 60 percent of employers provide an incentive to complete biometric screening, but less than 10 percent provide an incentive to take any action.

The numbers also drop off in other areas: About half of employers offer some form of incentive for completion of lifestyle modification programs (e.g., quit smoking, lose weight), and roughly 25 percent of those organizations using incentives/consequences strategies report offering incentives (monetary or nonmonetary) for progress or attainment made toward meeting acceptable ranges for biometric measures such as blood pressure, body mass index, blood sugar, and cholesterol.

While incentives can drive participation, not linking incentives to results is a slippery slope, the consulting firm fears. "Programs and tools like HRQs and biometric screenings can make employees more aware of their health status and of the opportunities to improve their health, but alone they won't move the needle when it comes to health improvement and mitigating cost," says Jim Winkler, chief innovation officer for Health & Benefits at Aon Hewitt.

"Incentives solely tied to participation tend to become entitlement programs, with employees expecting to be rewarded without any sense of accountability for better health. To truly impact employee behavior change, more and more organizations realize they need to closely tie rewards to outcomes and better results rather than just enrollment."