Depression and obesity are so closely related that it is difficult to tease apart the relationship between the two. A latest genomic study conducted on large scale adds evidence.
Depression and obesity are both significant health concerns. If the latest research is to be believed, these cost trillions of dollars to the global economy every year. Studies  conducted in the past revealed that depression is more common in obese or overweight people.
But observational studies can’t say if obesity is the cause for depression as there are many factors that must be considered. Obesity is a risk factor for a host of other health conditions and probably it could be that dealing with other health conditions increases the incidence of depression instead of obesity causing depression directly.
Some of the researchers have claimed that depression could be a risk for obesity . Others are of the view that obesity and depression aggravate each other . This is because initially obesity can increase the chances of depression but once depression sets in, it may exacerbate obesity by making it difficult for the person to exercise.
Relooking at Depression and Obesity
To understand the complicated relation, researchers from University of South Australia joined hands with researchers from University of Exeter in the U.K. The results were issued in “International Journal of Epidemiology.” 
Dr. Jess Tyrrell explains that depression and obesity are health concerns that impact lives and are expensive on health services. We know that there is a connection between the two, but we don’t know what causes the other; whether it is depression causing obesity or vice versa. Also, we don’t know if it is obesity causing depression or the health problems associated with obesity that cause depression.
The study made use of genetic data to examine the relationship between depression and obesity. Researchers wanted to know if a higher Body Mass Index (BMI) was associated with increase in the chances of having depression without the prevalence of other health conditions. Medical data was collated from 48,000 people having depression and compared with more than 290,000 controls making it a very large study for addressing the question.
Is It All Psychological?
As what is expected, higher BMI implies more chances of having depression. This correlation is more evident in women as compared to men confirming the findings. Women having a greater BMI had 21% more chances of having depression as against 8% in men
Researchers investigated people with genes that pre disposed them to obesity but not the ones that predisposed them to conditions like diabetes (termed as favorable metabolic profile) and this helped researchers tell apart the psychological component of obesity.
In the analysis, they reckoned variables that could impact the results like smoking, alcohol consumption, socioeconomic status and physical activity.
It was found that people with a favorable metabolic profile had the same likelihood of developing depression as those with obesity who carried genes that predisposed them to metabolic conditions. The effect was more noticeable in women.
To cross check the findings, they garnered data from Psychiatric Genomics Consortium and they got similar results thus adding more weight to the conclusion. So, they concluded that psychological impact of obesity can cause depression.
Dr Tyrrell says that these are important findings. This will help reduce depression which makes it difficult for people to adopt healthy lifestyle. The relationship between depression and obesity, however, remains twisted and the question still does not have an answer. The authors say that they cannot rule out the probable bidirectional casual relation between depression and obesity. But more research is needed to understand the relation between the two.
Obesity and depression have deep impact on the individuals and society in general, so the scientific community will continue to look at their connections.