A recent study published in Pediatrics compared activity levels of two groups of children given a Wii. There was 78 children, ages 9-12, who participated. Each child was given a new Wii console of which none had previously owned. One group of children were asked to choose one game that was fitness focused ie Wii Fit Plus. The other group of children were asked to choose one inactive game ie Mario Kart. The children wore accelerometers for 6 weeks. At the end of 6 weeks, they were allowed to choose one new game for an additional 6 weeks. At the end of the 12 week study, there was no difference in the level of activity between the two groups.
Reference: Marcus, M. Active' video games may not boost kids' fitness: study. Retrieved from Medical Xpress on 2/29/12 at http://medicalxpress.com/news/2012-02-video-games-boost-kids.html