WASHINGTON, D.C. -- Schools should be a cornerstone of the nation's obesity battle, but to trim Americans' waistlines, changes are needed everywhere people live, work, play and learn, a major new report says.Two-thirds of U.S. adults and almost a third of children are either overweight or obese, and progress to stop this epidemic has been too slow, the influential Institute of Medicine said in its report released Tuesday.Most of us know we should eat less and move more. But the institute makes clear this isn't just an individual but a societal problem: For a host of reasons, sedentary lives have become the norm and we're surrounded by cheap, high-calorie foods.The new report offers a roadmap of the most promising strategies to change that -- and argues that the solutions can't be implemented piecemeal."Each of us has this role. We can't sit back and let the schools do it, or let a mayor do it or think somehow the federal government's going to solve it," said report co-author William Purcell III, former mayor of Nashville, Tenn. "These recommendations require concerted effort among all."Still, the report says schools should be a national focus since they're where children spend up to half of their waking hours and consume between a third and half of their daily calories.Schoolchildren should get at least 60 minutes of physical activity a day -- a combination of physical education, recess and other activities, the report says. Many schools have slashed P.E. and cut into recess in recent years in an effort to increase learning time amid tighter budgets. The report also says schools should serve healthier foods -- backing school nutrition standards -- and teach students about good nutrition.Other recommendations include:--Restaurants should ensure that at least half of kids' meals comply with federal dietary guidelines, without charging more for the healthier options.--Healthier foods should be routinely available everywhere, from shopping malls to sports arenas.--More food companies should improve how they market to children.--To make physical activity routine, communities should be designed with safe places to walk.--Public and private insurers should ensure better access to obesity screening, preventive services and treatments.--Employers should expand workplace wellness programs.The Institute of Medicine, an arm of the National Academy of Sciences, is an independent organization that advises the government.