U.S. stay-at-home mothers spend 6.8 hours a day cooking, shopping and playing with children, 2.2 more hours than full-time working moms, researchers say. Lead author John Cawley of Cornell University\'s College of Human Ecology and colleagues said fathers whose partners worked a full-time shift of 8 hours spent 18 minutes more on those days with their children, while non-working fathers spent 42 more minutes with their children on days their wives\' worked an 8-hour day at her employer\'s. The findings were consistent across socioeconomic lines measured by the mothers\' education, family income, race and ethnicity, Cawley said. The findings might help explain some of the increase in child obesity because to make up for their lack of time, working mothers were significantly more likely to buy prepared foods -- takeout from restaurants or prepackaged, ready-to-eat meals from grocery stores -- which are generally less nutritious than home-cooked meals, Cawley said. \"It\'s inaccurate to pin rising childhood obesity rates on women, given that husbands pick up so little of the slack,\" Cawley said in a statement. \"Working moms spend less time with their kids, but they also spent less time on themselves -- they spent 31 fewer minutes sleeping and less time watching TV, at leisure and socializing.\" The study is to be published in the December issue of Economics and Human Biology.