Bringing home a shiny new Wii Fit or Dance DanceRevolution game for your kids won’t make their days any more active than if you’d brought them Mario Kart. That’s the finding of a study published today (Feb. 27) in the journal Pediatrics.

Previous research has shown that children in laboratory studies using “active” games – games that require players to move their whole bodies, rather than just buttons or triggers on a controller – can get the equivalent of moderate or sometimes even vigorous physical activity. But Tom Baranowski, Ph.D., a professor of behavioral nutrition at Baylor College of Medicine in Houston, wanted to test the games under “real world” conditions, to see if receiving a new active game made kids move more at home.

Baranowski’s team selected 87 children ages 9-12 who did not already have a Wii console at home, and had Body Mass Index (BMI) high enough to put them at risk for obesity as adults. Age 10 has been pegged by experts as a critical window for increasing physical activity, because that’s the age where an obese child’s risk of carrying their weight problems into adulthood skyrockets.

Researchers gave all of the participating families Wii game consoles and necessary extras such as mats, controllers and balance boards. Half of the children were then allowed to choose an active game (Active Life-Extreme Challenge, EA Sports Active, Dance DanceRevolution-Hottest Party 3, Wii Fit Plus or Wii Sports), while half got to choose an inactive game (Disney Sing It-Pop Hits, Madden NFL 10, Mario Kart Wii, New Super Mario Bros. Wii or super Mario Galaxy). After six weeks, all the children were allowed to choose another game from the same group.

Activity levels for all children were monitored during the 12 weeks they had their games using an accelerometer, a device that’s worn to measure acceleration and exertion. Researchers found that the children using the active games were no more physically active during the study than those using inactive games.

“We were quite surprised,” says Baranowski. “We expected that we would detect a modest increase in physical activity during week one [among kids with the active games], which would be lost by week six, and detect another smaller increase in physical activity at week seven (after just having received their second active video game) which would also die out by week 12.”

Baranowski and his team theorize that children receiving the active video games either didn’t play them very intensely, or they offset activity from the games by choosing to be less active at other times of the day. “I would bet a little bit of both,” he says. “We have qualitative data that indicated the kids did play the games and enjoyed them, but obviously they didn’t play them intensely enough.” He explains that without actual instruction to play the games at a certain intensity level, or for a certain amount of time each day, kids didn’t get enough physical activity from the games to make a difference.

But he also notes something about the make-up of active games that could be getting in the way of extended play. “By themselves these active video games have little to no story,” he says. “Wrapping a story around these games also holds promise,” as a way to hold kids’ attention for longer periods. A colleague is working on research to test that idea.

Meanwhile, don’t count on a game to give your kids the exercise they need. “You need to do more than just purchase and provide your child an active video game,” says Baranowski, who suggests playing the game with your child on a regular basis (even daily), adding other activities like a nightly walk to the family calendar, or getting your child involved in sports teams at school or in your community.