Bobby got used to being the biggest kid in class, his round figure dwarfing his classmates even in kindergarten. He learned to take it when the other kids called him fatsoæand other names he'd rather not repeat. He quietly sat out during kickball at school, even though he loves to play the game.

An estimated 20 percent of American children are obese. In fact, children in the U.S. face this problem in rising numbers. About 11 percent of 6- to 17-year-olds are obese, and twice that number are overweight.

Far from just a cosmetic problem, obesity is considered by some experts to be one of the greatest medical risks faced by children in the United States today.

Short- and long-term consequences may include diabetes, orthopedic problems, premature puberty, respiratory complications, hypertension, heart disease and certain cancersænot to mention low self-esteem.

In general, experts believe that there are some common causes of obesity among the young: lack of education about proper nutrition, paltry opportunities for exercise, too much TV, the glorification and overconsumption of fastfood. Perhaps more than anything, these problems are rooted in the family, in entrenched food purchasing, eating and activity patterns. In fact, many parents may be poor role models. More than one-third of adult Americans are overweight, and their children tend to take after them.

Parents must address the problem. The first step in helping a youngster is to take him or her to a physician for a full physical examination. Such an exam allows the physician to look for a medical cause for obesity. Although extremely rare, adrenal problems, thyroid disorders and even certain tumors can cause rapid weight gain in children.

Once possible medical causes of obesity have been eliminated, the physician can refer the child to a pediatric dietitian who will help set realistic goals for the child. In toddlers and young school-aged children, the goal should be to slow down weight gain and allow the child's height to catch up to his or her weight.

For students in junior high and high school, individual weight goals must be based on the degree of obesity and the stage of puberty . If weight reduction is necessary, the physician can help the patient set realistic goals and monitor weight loss.

When trying to help your youngster through this difficult process, remember that parental love and uncritical support are essential.

Dr. Sally Robinson is Professor of Pediatrics, and Dr. Keith Bly is Assistant Professor of Pediatrics at the University of Texas Medical Branch at Galveston Children's Hospital. For more information, visit: www.utmb.edu