Obesity and depression, not a great combo. A study on the relationship of genetic variants related to higher BMI and depression was published in the November 13 issue of the International Journal of Epidemiology. The said study strongly suggests that depression is caused by obesity and that depression is an unpleasant psychological effect of obesity that leads to mood disorder.

According to Professor Naveed Sattar of the University of Glasgow’s Cardiovascular and Medical Sciences Department, the recent study results can be considered as the strongest study thus far to suggest that higher weight can be a great risk factor of depression. It is similar to saying that depression and weight gain are directly proportional. 

Though Professor Sattar did not participate in the said study, he explained that even if there are plenty of reasons contributing to one’s depression, weight loss can indeed be helpful in improving one’s mental health, while being leaner, generally speaking, can decrease one’s chance of having depression. In essence, there is also a relationship between depression and weight loss. 

Causality between BMI and Depression

In order to know the path of causality between these two factors, researchers from the University of South Australia and the University of Exeter conducted a separate study wherein they examined various genetic data gathered from the Biobank in the UK, comprising of 291,995 individuals without depression and 48,791 individuals who were suffering from the said mental health condition. 

To unravel the relationship between depression and weight, and to also segregate the latter from other factors that can possibly muddle the results, these researchers used genetic predisposition to a heavier BMI as a substitute to one’s actual BMI. Though they have data for both, they prefer to adopt this kind of methodology to eliminate other possible factors that will affect the results. 

Two Different Genetic Variants and Depression

The researchers looked into two different variants of genes and its consequent relation to depression — genetic variants which are linked to higher BMI and also related to metabolic conditions like diabetes, and genetic variants which are linked to higher BMI but were also related to lower metabolic risk problems. 

According to them, if it was the corresponding health issue accompanying obesity that is making these obese individuals depressed, instead of the obesity itself, these genetic variants which are not accompanied by any type of metabolic baggage will not be related to depression. Then again, based on the results of their research, they found that depression was linked to the genetic variants that were also related to the lower metabolic threat. 

In their written study, the researchers wrote that the analysis was vital and significant because it means that higher BMIs bear adverse psychological and physiological effects that were driven as a result of the adverse metabolic condition. 


These studies all provide strong evidence to support the assumption that the link between depression and weight, in part, may be a result of a direct bearing of a person’s weight on his correlative depression risk. 

All these studies are complicated and have used various kinds of complex analyses to have a deeper look into the causality between depression, weight, and genetics. The study design used by the researchers remove any other factor that may compound the results and may change the locus of the same. Also, they were able to carry out various types of analyses to make sure their results were accurate and reliable. 

A specific example would be how they classified respondents into those having depressions and those who are not having such mental condition. Their classification may not be entirely accurate since their bases for categorization were based on past medical reports of people who seek professional help for anxiety, nerves, or depression. There may be people who had depression but opted not to seek professional help, and also people who might have been diagnosed with such condition, had they been assessed thoroughly. However, this is justified when the proponents of the study got the same results when they did not include people without any depression diagnosis written on their medical records. 

At the end of the day, even if these studies contributed greatly to the current body of knowledge linking depression to obesity, there is still a lot that needs to be learned and confirmed, said the National Health Service. For instance, the study’s findings suggest a psychological link, but they are yet to look deeper into how exactly obesity is a contributory factor to a person’s risk of depression. If you are overweight and you’re also suffering from depression or low mood, though this condition does not automatically mean you have higher risk factors, it would be best if you seek treatment for both conditions. 

At the end of the day, physical and mental health conditions are related and improvement in one aspect can lead to improvement on another. 

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