First of all, leave healthy choices out for snacks. Children tend to grab whatever is easiest and "there" - get rid of the fruit roll ups, chips and crackers and substitute those items with real fruits, carrot sticks or other veggies chilled and crunchy, and if your child likes a sandwich for an afterschool snack, make it a healthy one with fillings ranging from tofu to cheese to peanut butter.
Teach your child to watch portions. Once you start going over what a serving size actually is, your child may discover that he's actually been eating two or more servings of cereal or crackers at a sitting - those calories add up and the end result isn't good health. Start teaching your kiddo to make good choices now and they'll carry that lesson into their adult years.
Getting up and exercising is another way for kids to stay fit. In the colder areas of the United States, going outside and playing every day isn't an option so indoor activities have to . If your child enjoys playing video games or being on the computer - let him but limit those activities so they don't fore go healthier pursuits.
Teach your kids to make good choices with their foods and their bodies; in doing so you'll raise a healthy young person that make healthy decisions instead of another obesity statistic.