Over the past two decades, the number of overweight adolescents has tripled. The habits that lead to skyrocketing childhood obesity figures start early in life. According to a recently published study in The Lancet, the average 3-year-old gets just 20 minutes of vigorous physical activity each day, well short of the recommended hour a day for that age.

"Young children are the most active Americans of any age," says Frances Berg, childhood obesity expert and author of the book Underage and Overweight: America's Childhood Obesity Crisis – What Every Family Needs to Know (Hatherleigh Press, 2004). "Because young children naturally move around a lot, many people assume they are getting all the physical activity they need. But today TV and videos often keep them still for longer periods than parents realize."

Habits for Life
According to Berg, it's easy to start young children with active habits. "Young children love to run and play, but too many are stuck in the stroller, baby seat or playpen for long periods," she says. Her suggestion: Incorporate physical activity into your child's playtime.

"The idea is not to have baby workouts," she says. "Physical activity should be a fun part of daily life and never forced. If children begin to associate being active with having fun, they're more likely to stay active as they grow up."

Berg has the following tips for parents who want to start their children on a path to an active life:

1. Take a Break From Cartoons
From Big Bird to Spongebob, little children love television. It's not necessary to cut out TV time altogether, but it's important to mix it up with active playtime. Toddlers and preschoolers should not be sedentary for more than an hour at a time except when sleeping.

2. Remember Your Inner Child
Though it may be tempting to just sit and chat with the other parents at the park, getting up and playing with your child can be a fun way to bond. You'll set a great example for your child while getting some exercise yourself – and playing games with your child can be a great way to remember the fun of your own childhood!

3. Make Playtime Fun
It's very important not to force your child to engage in physical activity. When you propose a game of tag or peek-a-boo, it should be because it's fun, not because there's been too much sitting around that day. If physical fun seems like a normal part of the day, instead of a punishment for too much TV, children will look forward to it – an attitude that they will carry with them once they get old enough to make their own choices about playtime.

4. Babies Need Movement Too
Try not to keep an infant confined to a baby seat for long periods. Even when very young, children move differently when stretched out on a blanket than when strapped into a baby seat.

5. Get Caregivers Involved
If childcare is provided by a grandparent or other relative, express your interest that the child be active during the day. Though keeping up with an active child might be difficult for an older adult, even a slower activity, such as a walk around the block, is better than placating the child with television or a video – and it can be a great way to get the grown-up moving, too!

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