When is a child too old to ride in a stroller?

You can't swing a Pop Tart without hitting a new report about the childhood obesity epidemic. And recess and gym are no longer a given at many schools. So building in exercise whenever you can is a must, says pediatrician Jennifer Trachtenberg, author of "Good Kids, Bad Habits" (Collins, $21.95). That includes more walking.

"Definitely by age 4, and I hope to start at age 3, make a stroller not their major mode of transportation," Trachtenberg says. "Hoofing with your feet is really important at a young age."

Trachtenberg says 70 percent of our overall health is tied to our lifestyle choices (like getting enough exercise), and the habits you form as a youngster are likely to stay with you for life.

If your child is resistant to walking, Trachtenberg suggests making it more fun. "Practice counting, look for things that are a certain color or start with a certain letter," she says. "It's also a great way to take a few extra minutes and talk about the day."

She says scooters, bikes and skates are also great options, as long as a helmet is in the mix.

"The key is moving," she says. "Kids should get a good hour of moving around a day, even if it's broken into spurts."