Obesity’s link to depression tied to both physical and social factors

EXETER, United Kingdom — New research out of the United Kingdom is further re-enforcing the connection between weight issues and mental health. While this isn’t the first study to establish a connection between obesity or high body mass index (BMI) and depression, a team from the University of Exeter set out to answer how exactly a high BMI leads to depressive symptoms. Study authors report that a combination of both physical and social factors are likely at play.

Studies have linked excess weight to an increased risk of heart attack, stroke, and diabetes for decades. More recently, however, new studies have established a connection between obesity and poor mental health. Study authors conducted this new research in an effort to find out whether the link between high BMI and depression is a psychosocial or a physical reaction.

Psychosocial pathways include the social stigma or shame that many may feel about being overweight around others in better shape. There is also a societal perception that everyone should be skinny or in shape. Meanwhile, physical pathways are metabolic conditions with a historic connection to a high BMI, such as type 2 diabetes or high blood pressure.

Regardless of disease, weight impacts mental health

The team analyzed genetic data on over 145,000 people originally collected for the U.K. BioBank project during this study. They also examined any available mental health information from participants as well. Study authors then analyzed genetic variants associated with higher BMI in conjunction with scores on a clinically-relevant mental health survey put together to assess depression, anxiety, and well-being levels.

Obesity and depression are both major global health challenges, and our study provides the most robust evidence to date that higher BMI causes depression. Understanding whether physical or social factors are responsible for this relationship can help inform effective strategies to improve mental health and wellbeing,” says co-lead study author Jess O’Loughlin from the University of Exeter Medical School in a release. “Our research suggests that being fatter leads to a higher risk of depression, regardless of the role of metabolic health. This suggests that both physical health and social factors, such as social stigma, both play a role in the relationship between obesity and depression.”

Finding a genetic link between weight and mental health

To determine which pathways specifically lead to depression among overweight individuals, researchers also analyzed two recently discovered genetic variants. The first of those variants promotes obesity, albeit a much more metabolically healthy version of obesity. So, people with that set of genes may be overweight, but they’re actually much less likely to develop high blood pressure or other conditions. The second set of genes causes a more traditional version of obesity that’s linked to various metabolic problems.

Interestingly, study authors noted very little difference between the two variants, indicating that both social and physical elements play into the obesity-depression relationship.

“This is a robust study, made possible by the quality of UK Biobank data. Our research adds to a body of evidence that being overweight causes depression. Finding ways to support people to lose weight could benefit their mental health as well as their physical health,” concludes co-lead study author Dr. Francesco Casanova.

The study appears in the journal Human Molecular Genetics.