BAKERSFIELD, Calif. -- Nearly 1 in 5 American adolescents is overweight or obese, but encouraging teenagers to lose weight can be a tricky business.

Adolescents are particularly vulnerable to eating disorders, and so adults must choose their words carefully. New research on more than 2,500 middle and high school students has found that one of the best ways to help kids is to eliminate the word "diet" altogether.

Telling teenagers to diet often backfires, the study shows. Adolescents who are self conscious about their weight are more likely to turn to dangerous behaviors such as taking diet pills, skipping meals or self-induced vomiting.

Researchers suggested doctors tell young patients that extreme dieting can actually add pounds to discourage them from trying these practices.

Teenagers with poor body image gained the most weight in the study, so experts said parents should not criticize their children's weight.

Instead, families should focus on healthy eating and enjoying physical activities together, such as bike riding or ball games in the backyard.