Background Many studies have reported the association between overweight and depressive status during puberty. Recently, it has been suggested that this association is affected by a person's image of their body which differ between gender and nationality. Although these associations were mainly examined by cross-sectional study, this study aimed to examine the relationship between change in weight and developing depression, taking into account gender in this prospective cohort study.

Method In 2007, a community-based cohort study was conducted with 1347 children in grades 4–7. Height, weight, depressive status and body image were surveyed at the baseline and at the 1-year-follow-up. Over weight and having depressive symptoms were defined using international cut-off points. Multiple logistic regression analyses were conducted to examine the effects of weight status and body image on developing depression by gender.

Result The follow-up rate was 89.1%, and 6.9% of these children experienced depressive symptoms at follow-up. Some boys who continued to be dissatisfied with their body weight as overweight were more likely to develop depression compared with those who were satisfied with their body weight (OR, 2.5; 95% CI 1.0 to 6.0). On the other hand, some girls who continued to be satisfied with their body weight were significantly less likely to develop depression. In both genders, body image caused a more increasing risk for depression than weight status.

Conclusion This study suggested that body image effected the association between weight status and depression; those effects might be affected by gender difference.