Researchers said that this is one of the first studies to explore a possible link between victimization and weight changes for obese adolescents.
During the study, principal investigator Ryan Adams, assistant professor of educational studies at the University of Cincinnati, and William Bukowski, professor of psychology at Concordia University in Montreal, Canada, examined peer victimization as a predictor of depression and body mass index in obese and non-obese adolescents.
Adams said that while peer victimization is comparable to bullying, bullying behaviour typically involves one-on-one targeting while peer victimization can also entail victimization that can come from the peer group in general.
Over a four-year period, researchers found lower self-esteem and increased depression and body mass index in obese females, who felt their peers victimized them.
Obese males reported increased depression and lower feelings about physical appearance.
However, negative feelings about their physical appearance earlier in the study were linked to a decrease in body mass index as they got older.
In case of non-obese males and females, there was no association between peer victimization and increased body mass index, but there were links to negative feelings about physical appearance as they got older.
"Victimization may not only reinforce the negative self-concepts that a risk factor for victimization, such as obesity, may cause, but a risk factor for victimization, such as obesity, will also make it more likely that the adolescent will be victimized indefinitely," Adams said.
"In other words, the risk factors that strengthen the links in this pathway will also keep the pathway intact because it is also a risk factor for being victimized," he added.
Using data from Statistics Canada (Canada's national statistical agency), the researchers randomly selected Canadian children identified through the National Longitudinal Survey for Children and Youth and gathered self-report data from 1,287 participants over three different time periods, including when the children were 12-13 years old, 14-15 years old and 16-17 years old.
To determine if children were being victimized by peers, they were asked whether children said nasty things to them at school, whether they felt bullied at school, or if they were bullied on the way to or home from school.
To examine feelings about their physical appearance, researchers asked children whether they liked the way they looked.
To check body mass index over the three time periods, the children were asked to report their weight and height. Body Mass Index (BMI) was then calculated for males and females, and obesity was determined based on the Centers for Disease Control and Prevention's growth charts.
"The current study suggests that a risk-factor for being victimized, such as obesity, may play an important role in the long-term effects of victimization by making it more likely that the adolescent will be victimized over the long term, but also that victimization can reinforce the negative self-perceptions that the adolescent already has," Adams said.
"It is important to go beyond using obesity as a predictor of long-term adjustment and examine the processes and experiences of obese individuals that might cause depression or changes in health," he added.
The study is published in the current issue of the Journal of Child Psychology and Psychiatry.