Kids today don't spend enough time playing video games—at least, not the kinds that get them off the sofa. Several recent studies have found that playing active video games such as Dance Dance Revolution keeps the pounds off and improves fitness levels. As researchers continue to quantify the physical benefits, manufacturers plan to capitalize on the results, not only by releasing new titles and systems, but also by installing them in schools and pitching them to pediatricians in hopes that they will urge patients to use them.

Over the years, investigators have accumulated evidence that some traditional video games can sharpen the mind. Just last December, a study in Psychology and Aging found that playing strategy-type video games can help older people retain certain cognitive skills that tend to decline with age, such as reasoning and switching between tasks.

But more recently, studies exploring the effects of games that require players to do more than sit in one place have revealed how the diversions can improve the body. Among the latest work to connect weight loss in kids with video entertainment comes from Robin Mellecker and Alison McManus of the University of Hong Kong. In the September 2008 issue of Archives of Pediatrics & Adolescent Medicine, they report that elementary school children who played video games for 35 minutes a day could burn around 150 calories, enough to prevent weight gain in an average-weight child. The discovery echoes similar findings published in Pediatrics in December 2006, which found that super active video games can work as well as traditional play time in terms of energy expenditure.

The Hong Kong study used a game system relatively unknown in the U.S. but popular in Asia, called XaviX. McManus says that she and Mellecker chose XaviX, made by SSD Co., Ltd., of Japan, "because it is much cheaper than any of the other alternatives." In the most active game, J-Mat Jackie's Action Run, players run or walk on a special mat that represents the streets of Hong Kong, "occasionally dodging barriers in the road by sidestepping, squatting, jumping, and stamping out the virtual ninjas," Mellecker and McManus wrote in their study.

Other researchers have looked at active games popular in the U.S., too, and drawn similar conclusions about their physical benefits. The systems include Dance Dance Revolution, which requires players to step on sections of a pressure-sensitive mat as ordered by arrows on a screen, and Nintendo's Wii and Wii Fit, in which players can try their skill at simulated bowling, tennis and other sports and exercises.

Despite the results, not every parent or pediatrician thinks encouraging active video games is a great idea. "Once you say to a child, 'We really want you to play these video games,' will they then become more enamored with entertainment games?" including ordinary passive ones, asks Donald Schifrin, a Seattle pediatrician who is also vice chair of the American Academy of Pediatrics committee that deals with media and children's health. He worries about a child saying, "My parents told me that a gaming system is good for me."

Peter Newman, general manager of XaviX's manufacturer SSD, insists that his company is sensitive to that concern. Real sports should come first, he says. "But when it's minus 40 in Minneapolis or over 110 in Phoenix, you can still stay active" by playing XaviX, he says. He also advocates the video games for "kids who are not athletic—kids who were last to get dressed for PE."

The games "can be one of the many tools to combat childhood obesity," agrees Heather Snavely, a director in Microsoft's interactive entertainment unit, but "it's not one or the other." Snavely says she monitors her two children to make sure they divide their time between screens and outdoor play.

A number of schools seem to have decided that when it comes to video games, if you can't beat 'em, join 'em. West Virginia has provided Dance Dance Revolution to all 160 middle schools and more than two thirds of its 592 elementary schools, according to Melanie Purkey, executive director of the state Office of Healthy Schools. (At the high schools, Purkey concedes, "they want the newer games," like those that appear on Wii.) She says the games are so popular that teachers use them in before- and after-school programs in addition to physical education classes. Meanwhile, Newman claims to be working with "thousands of schools" and other institutions around the world, including senior centers and gyms to tap into the adult market.

Not surprisingly, SSD and Microsoft are eager to tout the scientific findings to build market share. Newman is preaching the benefits to pediatricians, whom he hopes will pass the word to parents who might buy SSD games for their kids. Snavely notes that Microsoft brought out two new action games in November: Lips, in which players can gyrate and dance along with a rock band; and You're in the Movies, where a video camera films players while they pretend to chase villains or practice kung fu—or take on more passive roles, like screaming.

For that matter, the Hong Kong researchers even hope to market their own game, "a walking media station" that consists of a treadmill, keyboard and flat-screen TV, McManus says. The idea is that kids could be doing all their texting and Web surfing while striding—a game that seems more like real life than a game. At least they won't have to worry about walking into a tree.