The first study to actually measure fitness levels in a representative sample of Americans is out, published in JAMA today. And there's no more room for denial: based on the results, about 20 percent of Americans aged 12 to 49 are out of shape and at greater risk of disease and early death. That's about 16 million people.

The worst of it is that adolescents are even more out of shape than adults -- close to a third of teens flunked the fitness test, which translates into 7.5 million adolescents wheezing their way through a treadmill test.

Given that the daily lives of most teens are seriously constricted within the framework of school, homework, and school-related activities, adults are going to have to accept a big share of the blame for the flabby condition of our young people. Parents and educators, unite! We've got to get these kids moving. Whatever it takes: pressure schools for a return to daily PE, and help them find the money to do it right...give kids some kind of reward (not candy!) for walking to school...get rid of the leaf-blower and the snow-blower, and hire kids to rake and shovel instead. Set and enforce limits on TV, computer and game system use, and don't let the whining get to you.

Some experts believe that we are on the verge of seeing lifespans in this country actually decline, pulled down by all that excess weight we're carrying around. Obesity and poor conditioning could outpace medical and scientific advances within the next few decades to shorten our children's lives.