More than half--56 percent--of the companies surveyed said that morale among their workforces has gone up as a result of their fitness initiatives. Another 27 percent said they have saved money on the cost of health care. About two out of 10 experienced increased worker productivity and decreased absenteeism.

LuAnn Heinen, director of the Institute on the Costs and Health Effects of Obesity, says that obesity costs U.S. employers more than $13 billion annually. On-site company fitness centers and other fat-fighting initiatives are designed to stem those costs.

Not all employees are enthused. The Business Group study found that in about two-thirds of companies, fewer than 25 percent of employees participate in their fitness programs.