Americans are facing an epidemic of overweight children. An estimated 20 percent of all children today are obese — which means they are 20 percent above what is considered to be the normal weight for their height and age.

Many parents don't realize the physical and emotional obstacles that being overweight can create. The condition can lead to medical problems in childhood, including high blood pressure and cholesterol, sleep apnea and joint problems. Obesity can also increase the risk of cancer, diabetes, heart disease and other disorders in adulthood.

Often, overweight children are teased by their peers and may develop poor self-esteem as a result. Such children may avoid or have trouble succeeding in sports.

Who or what is to blame for the current epidemic? Genetics plays a role in obesity, so any child with overweight parents is at risk. But in our country, children often become overweight as a result of their diet and lack of exercise.

Many children eat too many fast foods and processed foods, which are full of unhealthy fats, sugars and salt in oversized portions. These meals also are made up of nutritionally "empty" calories that don't supply a balance of necessary nutrients.

It's all too easy for busy parents to fall into the trap of giving children too much of the quick, convenient junk food they ask for. Healthier foods, with more fiber and protein, are not the ones being pushed in television advertisements. These also take more time to prepare and may be more expensive.

Added to our unhealthy diet is our couch-potato culture. Television, video and computer games and the Internet take time away from physical activity. As fields and forests are taken over by malls and housing developments, more children are spending too many hours indoors — often in front of the television. They're not getting the physical activity their bodies need.

In some cases, additional factors may contribute to weight gain. Some children turn to food for comfort, particularly if they have never found other ways to soothe themselves.

Some children may never have learned to pay attention to hunger and fullness cues. This seems to be more common in children who never sit down for relaxed mealtimes with their families. Instead, they have lunch or dinner while watching television, and they snack all day.

Children are more likely to learn to handle their appetites when mealtimes (and snacks) occur at regular, predictable times that have a beginning, middle and end — such as salad to start, then the main course, and finally dessert.

If you are concerned about your child's weight, let your pediatrician know — early. Your child's doctor should be monitoring your child's growth at each routine preventive visit.

A child under the age of 2 who is overweight is cause for concern. Such a child is likely to be obese later in life. Uncommon medical causes of weight gain, including hormone abnormalities, need to be considered.

Many children gain a little weight just before entering puberty. Unless the gain is excessive, parents shouldn't worry too much about it. Children this age are often very sensitive about their appearance, and a parent's reaction to bodily changes can be upsetting.

Try not to comment on it. If you are concerned, discreetly ask for your pediatrician's advice at your child's next visit. If your child is concerned, listen to him and let him know that you understand it bothers him. But be sure to tell him that this is a normal change and that you're not worried.

Your child won't be interested in changing her eating or exercise habits if she feels hurt by any suggestion from you that she is overweight. Instead of starting with your concerns, listen to hers. She may tell you that children at school tease her, that she can't run as fast as she wants to or that she's embarrassed by having to wear "husky-size" clothes.

If a child comes to you with such concerns, ask her, "Would you like to try to work on this?" If she says no, then simply say, "If you ever do, there are some things that can help. Just let me know when you're ready."

Meanwhile, try to set examples of healthy eating and physical activity yourself. These measures should be for all family members — not just the overweight child.

But if your child says she is ready, you can talk about the kinds of foods that will help her feel healthier and those that she might want to cut back on. Let her know that she doesn't have to go without food when hungry.

You might even suggest finding an exercise program that she'd enjoy.

As you begin to help, continue to make sure that this is her idea, not yours. If you can help your child discover her own motivation to overcome this challenge, she's far more likely to succeed.

Questions or comments should be addressed to Dr. T. Berry Brazelton and Dr. Joshua Sparrow, care of The New York Times Syndication Sales Corp., 122 E. 42nd St., New York, N.Y. 10168. Questions may also be sent by e-mail to: Questions of general interest will be answered in this column. Drs. Brazelton and Sparrow regret that unpublished letters cannot be answered individually. Responses to questions are not intended to constitute or to take the place of medical or psychiatric evaluation, diagnosis or treatment. If you have a question about your child's health or well-being, consult your child's health-care provider.