Americans Abandoning National Parks(r activities may get less sunshine and t...),Health

And, while America is "clearly a sedentary society," he doesn't believe an extra visit or two to a national park will cure America's obesity problem.

But Zaradic believes the problem runs deeper than that. "We tend to underestimate how important it is for ourselves and for our kids to get out and play in the dirt and to vacation somewhere like a state park or national park," she said. "We have forgotten how important our relationship with the real world is for our well-being."

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If you want to buck the trend and head outdoors, visit the National Park Service.

SOURCES: Patty Zaradic, Ph.D., Environmental Leadership Fellow and conservation ecologist, Bryn Mawr College, Bryn Mawr, Pa.; Oliver Pergams, Ph.D., research assistant professor, Department of Biological Sciences, University of Illinois at Chicago; Marc Siegel, M.D., internist and associate professor, medicine, New York University School of Medicine and Medical Center, and author, False Alarm: The Truth About the Epidemic of Fear; Feb. 4-8, 2008, Proceedings of the National Academies of Sciences