exercise

We're constantly hearing messages that we're eating too much and not moving around enough. Now researchers suggest that we're actually not eating more than we did 20 years ago, it's that we're much less active. And that includes not just middle-aged workers tied to their desks, but also young men and women who spend their days sitting in front of their laptops.

When Dr. Robert Zarr wanted a young patient to get more exercise, he gave her an unusual prescription: Get off the bus to school earlier.

"She has to take a bus to the train, then a train to another bus, then that bus to her school," says Zarr, a pediatrician at Unity Health Care, a clinic that serves low-income and uninsured families in Washington, D.C. So the prescription read: "Walk the remaining four blocks on the second bus on your route to school from home, every day."

If you think that teenagers are becoming weaklings, you're right.

Less than half of youths ages 12 to 15 are even close to being aerobically fit, according to data released Wednesday by the Centers for Disease Control and Prevention.

That's down from 52 percent of youths in 1999 to 2000, the last time this survey was conducted. It measures "adequate" levels of cardiorespiratory fitness, which children need not only for sports but for good health.

And that was true regardless of a child's race and family income.

Of all the things parents worry about when it comes to their children's health, high cholesterol probably isn't very high on the list.

The more you sit, the less physically active you are, which can lead to all sorts of health problems, including an early death.

But too much sitting increasingly looks like a health risk all its own. Researchers at Northwestern University say that for people 60 and older, each additional hour a day spent sitting increases the risk of becoming physically disabled by about 50 percent — no matter how much exercise they get.

Sure, you think, my kid's on a football team. That takes care of his exercise needs, right? Probably not.

"There are these bursts of activity," says Jim Sallis, a professor of family and preventive medicine at the University of California, San Diego. "But if you think about it, one hour of playing football out on the field means that the vast majority of that time is spent standing around waiting for the next play."

We all know we're supposed to exercise daily, but precious few of us do. And it only seems to get harder with age.

There's a reason to try harder, though. Tacking more years of good health on to your life may be as simple as mowing the lawn more often and engaging in other everyday physical activities.