Mike Bowling, a network administrator at Discovery Communications, spends a typical day at his Silver Spring, Md., office troubleshooting E-mail systems, restoring data, maintaining network security--and crunching out dozens of push-ups and sit-ups. He and his fellow competitors in the company's fourth annual Body Challenge meet after hours for "Boot Camp" class with "the Sarge," who pummels them into shape during an hour of calisthenics, weight training, and running. "I could only do about 10 sit-ups and 20 push-ups last month, but now we're doing 70 to 100 push-ups in every class and about 150 sit-ups," says Bowling, 35, who is also running wind sprints for the first time since high school. He's down 13 pounds since January.

As the cost of employee healthcare grows by 10 percent or more each year, corporate America is instituting preventive measures: everything from Pilates class to belly dancing to lavishly equipped gyms. "We are trying to do whatever we can to encourage employees to stay healthy," says Evelyne Steward, vice president of Discovery's LifeWorks department, whose wellness program consists of health and nutrition classes, weight-loss groups, and an on-site clinic as well as the eight-week-long Body Challenge. Other fitness offerings include a 20-minute, low-sweat "executive workout" and yoga classes. Last year, 66 percent of companies surveyed by the Society for Human Resource Management offered wellness programs, up from 53 percent in 2001. The number offering weight-loss programs like Weight Watchers grew from 17 percent to 29 percent; while companies aren't rushing en masse to outfit their own gyms, more than a third now subsidize the cost of fitness club memberships.

Bottom line. Investing in fitness can provide an immediate return. In the first two years of the Body Challenge, the 800 or so (of 6,000) Discovery employees participating lost a collective 4,600 pounds; these and less dramatic results from across the wellness program "have had a positive impact on our health insurance costs," says Steward. Clif Bar, the energy-bar maker in Berkeley, Calif., spends about $1,000 per employee each year providing about 150 staffers with a free gym, three personal trainers, 24 classes a week, and a paid 30-minute workout break every day. "I consider it money very well spent," says David Jericoff, executive vice president of people, noting that yearly savings in insurance premiums are in the "double-digit percents."

"The investment is very small, and the returns are large," agrees Andrew Scibelli, head of health management programs at Florida Power & Light Co. in Juno Beach, Fla., whose fitness programs cost the company less than $100 per employee. FPL tracked results for five years after the 1991 launch and saw a drop-off in insurance claims for cardiovascular disease, cerebral vascular disease, and some cancers. More recently, the weight management program has proved itself as a way to help workers control their diabetes. A 2005 survey by consulting firm Watson Wyatt Worldwide of more than 500 companies found that those most serious about prodding workers to get healthy saw healthcare costs rise just 5 percent over two years; at the other end of the spectrum, increases ran as high as 11.5 percent.