NEW YORK — To set their children on a path to a long, healthy life, most parents diligently follow vaccination schedules, buy the latest and greatest safety innovations and wash their hands probably more times than necessary.

They also urge their kids to eat all that's on their plates, read books and allow their artistic sides to flourish.

All this is important, but so is physical activity and learning about healthful eating habits, says Melinda Sothern, a clinical exercise physiologist and director of the Pediatric Clinical Research Section at the Louisiana State University Health Sciences Center.

Unfortunately, many parents don't think about diet and exercise for kids until weight is already a problem.

"When kids become overweight 'all of a sudden,' parents don't understand how it happened," says Sothern, co-author of "Trim Kids" (HarperCollins) with T. Kristian von Almen, a research psychologist and assistant clinical professor in pediatrics at LSU Health Services Center, and Heidi Schumacher, the chief clinical dietitian at Children's Hospital in New Orleans. What parents don't realize is that "all of a sudden" was probably years in the making.

Until children turn 6 years old, their actual weight doesn't matter, but from 18 months on they are forming the behaviors and routines that will stick with them, often for life, explains Sothern.

A big turning point is when they enter kindergarten, when parents no longer control lunchtime and snacks and when kids don't spend the bulk of their day playing in the back yard.

"At school, kids are sedentary. At home, they're sedentary, watching TV or playing on the computer. The logical outcome is overweight kids," Sothern says.

The next critical phase is puberty, especially for girls. Not only is puberty a time when fat naturally accumulates on the body, but girls start spending their afternoons and evenings gabbing on the phone, Sothern observes.

She adds: "It's not the parents' fault. It's a societal problem that they don't have enough opportunities to be active and, as a sign of our success, there's an overabundance of food."

The burden, however, is on parents to find the solution.

"As a parent, you have to be a role model and lead a healthy lifestyle," says Mike Brungardt, the strength and conditioning coach for the professional basketball San Antonio Spurs.

Brungardt co-produced a children's workout video with his brothers Kurt, the author of health and workout books, and Brett, the strength and conditioning coach for the Dallas Mavericks. "Action Sports Camp" features former NBA All-Star Sean Elliott and is endorsed by the American Heart Association.

To get children moving, especially when they say they're tired after a day at school, is to make moving fun, says Kurt Brungardt.

"Have a dialogue about what your kids like and like to do," he advises.

Physical activity doesn't have to mean playing sports, adds Mike Brungardt. And change the routine often, varying the activities to retain interest.

"Any exercise 'routine' gets old, it becomes stale," says Mike Brungardt, and there also are physiological benefits in having a variety of activities and new challenges.

Hiking, biking, climbing trees in the back yard or playing tag with friends all accomplish the same goal as basketball: exercise.

Some kids simply are less interested in physical fitness, and their parents owe it to them to find these fun, active activities, Sothern adds. Their children may be putting on weight without overeating, she explains, but if they're not burning the calories that go into their mouths, it's as if they are overeating.

Either poor nutrition, a lack of activity or a behavior issue is driving a child toward an unhealthy weight, she says, "and one literally feeds the other."

Sothern has worked with more than 2,000 kids, and she says among the lessons she has learned in helping children achieve a healthier weight are never to impose adult exercise rules and not to restrict foods, making them a forbidden fruit.

If children are encouraged to enjoy physical play, not forced time on a Stairmaster, they will feel the euphoria that accompanies the rush of moving around and that hooks them into other activities, Sothern says.

As for food, she suggests parents redirect their children toward healthy foods and eating habits.

Her advice: Tell young children that eating vegetables will help them grow; tell teenagers that drinking a lot of water will help keep their skin clear; and don't leave serving platters on the table, which invites everyone to eat seconds.

Also, always eat meals and even snacks at the table, which will limit opportunities to graze, and stay away from anything "super size," which is too big for anyone.

"The best motivation for parents to get healthy is that they want healthy kids," says Kurt Brungardt.