Michael & Susan Dell Center for Healthy Living faculty member Dr. Robert Roberts and colleague Dr. Hao Duong with HAIVN: Partnership for Healthy Advancement in Vietnam sought to answer this question by examining a potential mediating factor linking depression and obesity: body image.
In their article titled “Does major depression affect risk for adolescent obesity,” published in the Journal of Affective Disorders last July, the investigators address a previous study that suggested that the relationship between depression and obesity was not a direct one, but rather an indirect relationship through other, unknown processes or factors.
Looking to several studies that identified poor body image as a risk factor for psychological distress, Drs. Roberts and Duong designed their investigation to search for a temporal relationship between depression, body image and obesity among Houston youth.
The authors used DSM-IV diagnosis to identify depressed study subjects, and body mass index (BMI) was used to classify subjects as normal weight, overweight or obese. The researchers then looked at “perceived body weight” to determine good or bad body image.
This is where it gets tricky. To see whether or not body image was indeed a mediating factor between depression and obesity, the investigators tested the association between four models: (1) Whether depression predicts obesity, (2) whether depression predicts body image, (3) whether body image predicts obesity, and (4) whether controlling for body image weakens or removes the connection between depression and obesity.
After running the data through this model, the authors revealed some interesting findings. Like in their previous study, major depression was found to predict obesity (1). However, major depression did not predict good or bad body image (2).
Taking depression out of the picture, body image was found to significantly predict obesity but only in girls. (3) The authors discovered that when girls perceived themselves as being overweight, it was very likely that they would be overweight years down the road. However, when looking at the crude rates, that is, before adjusting for other variables, poor body image increased the risk for obesity at follow-up 30-fold for the whole sample, 40-fold for girls.
But here is the kicker: The association between depression and obesity disappeared when the analysis mediated for body image, overall and by gender, confirming the author’s hypothesis that the link between depression and obesity operates through body image. (4) So what does this mean?
Drs. Roberts and Duong interpret the results of the study to suggest that “poor body image is the exposure increasing the risk for obesity,” not depression. Although a relationship between depression and obesity has been previously identified, this study prompts researchers to explore other mediating factors, like body image, that may dissolve that relationship.
This investigation has great implications that can be applied to public health practice. Clinical interventions aimed at addressing obesity should consider adding activities that seek to improve body image of participants to help kids and teens have healthy bodies and healthy minds.
Kayla M Albrecht
2nd Year MPH Candidate
UT School for Public Health Austin Regional Campus