About 95 percent of large employers (with 200+ employees) and about a third of smaller ones offer programs to improve the health of workers, reports The Washington Post.

But many programs are small and limited because evidence of a dollar-and-cents payoff for employer fitness is missing.

Why do many companies take only baby steps when it comes to employee wellness?

Employee interest in wellness programs is generally low, according to the Department of Health and Human Services.

Most payback studies tend to be short in duration and are not random, so results might be skewed.

Study results often relate only to specific workforce demographics, location and workplace culture. Programs have little value if they can't be duplicated at another location.

A serious study of workplace wellness programs is costly. Some costs, such as health care utilization and absenteeism, are easily quantified, but others — such as the impact of having sick workers show up for work but perform below par — are not.

Most employers who study the effectiveness of their wellness programs seem to have a bias in favor of the effort. Studies that show little or no benefit for the employer are likely to get buried, says one expert.