Overweight adolescents are more likely than normal-weight children to be victims of bullying (search), or bullies themselves, a study found, bolstering evidence that being fat endangers emotional as well as physical health.

The results in a study of 5,749 Canadian youngsters echo data from British research and follow a U.S. study published last year in which obese children rated their quality of life as low as young cancer patients' because of teasing and weight-related health problems.

While not surprising given the stigma of being overweight, the new findings underscore the importance of enlisting teachers and schools in the fight to prevent and treat obesity in children, said lead author Ian Janssen, an obesity researcher at Queens University (search) in Kingston, Ontario.

"Anybody's who's ever been on a playground would know" that overweight children are among those who get picked on, Janssen said, adding that in some cases, that may lead the youngsters to become bullies themselves.

The study appears in the May edition of Pediatrics, released Monday.

Janssen said obesity rates in Canadian children tripled from the 1980s to 1990s and show no signs of slowing down, similar to rising rates in other developed nations and in the United States, where 15 percent of school-age youngsters are obese and increasingly plagued by related health problems. Nearly one-third of American children are overweight.

The toll on emotional health is just as worrisome, the researchers said.

"The social and psychological ramifications induced by the bullying-victimization process may hinder the social development of overweight and obese youth, because adolescents are extremely reliant on peers for social support, identity and self-esteem," the researchers said.

Their data is based on a national survey of Canadian youngsters, ages 11 to 16, conducted in 2002.

Among normal-weight youngsters, almost 11 percent said they were victims of bullying, compared with 14 percent of overweight youngsters and nearly 19 percent of obese youngsters.

About 8 percent of normal-weight children said they were perpetrators, compared with 11 percent of overweight youngsters and 9 percent of the obese children.

Obese boys and girls were more than two times more likely than normal-weight youngsters to be victims of "relational" bullying — being intentionally left out of social activities. Obese girls were about twice as likely to be physically bullied on a weekly basis than normal-weight girls; among obese boys the risk was slightly lower but still substantially higher than for normal-weight boys.

Obese girls were more than five times more likely than normal-weight girls to physically bully other youngsters at least once weekly. Among boys the risk of being physically aggressive was only slightly increased, but they were more than twice as likely to make fun of others and spread lies and rumors than normal-weight boys.

Cleveland child psychologist Sylvia Rimm, author of "Rescuing the Emotional Lives of Overweight Children," (search) said many schools with anti-bullying programs don't specifically address overweight youngsters.

Rimm said reducing bullying could help youngsters overcome their weight problems. Bullying perpetuates those problems because it isolates them, and "the only thing left for overweight kids is food and television," she said.