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Heavier Burden: Landmark Study Reveals Weight's Impact on Mental Health in Ireland

Written by Andrew Le, MD

UpdatedMarch 27, 2024

The medical journal from PLOS ONE presented a thorough investigation into the link between body fatness, which they term "adiposity," and mental health, specifically addressing depression and overall well-being. The study was interested in exploring this connection in middle-to older-aged adults in Ireland, where evidence on the matter is somewhat scarce.

The study pooled a diverse group of 1821 men and women, ranging in ages from 46 to 73, finding them through random selection from a large primary care center's database. Researchers used two widely accepted tools to measure the mental health of participants: the 20-item Centre for Epidemiologic Studies Depression Scale (CES-D) for depression, and the World Health Organization-Five (WHO-5) Well-Being Index for overall well-being.

In terms of methods, the scientists undertook what's known as a cross-sectional analysis. This means they captured data at a single point in time instead of following subjects over a period. They looked at relationships between participants' mental health scores and their adiposity, the latter being quantified using two common metrics: Body Mass Index (BMI), which relates weight to height, and waist-height ratio, a measure that specifically pinpoints central obesity, which is a concentration of fat around the abdomen.

One of the study's key strengths is its meticulous approach to data analysis. They not only looked at simple associations but adjusted for various other factors that could influence the outcomes. These included demographic details like age and sex, lifestyle factors such as smoking and exercise habits, and the presence of certain disease conditions that are known to impact both mental health and adiposity, like diabetes and heart disease.

The results of the study are both meaningful and concerning. Both BMI and waist-height ratio exhibited a significant positive association with depression scores among all participants. On the other hand, they had a negatively significant association with well-being scores, which means that as adiposity increased, reported well-being decreased. These relationships stayed consistent even after the data was adjusted for demographic and lifestyle factors.

The study dove deeper and adjusted the models once more for disease conditions. The findings did not budge—increased adiposity was still robustly related to higher depression scores. When they broke down the data by gender, they observed that these relationships were more pronounced among women than men, but not to an extent that statisticians would call a modifying effect.

From their findings, the researchers drew a concerning conclusion: Higher levels of body fat are linked to poorer mental health, regardless of lifestyle habits or existing diseases. Reflecting on the implications, they suggest that interventions aimed at curbing depression should seriously consider incorporating strategies to manage and reduce obesity at a population level.

It's fundamental to acknowledge the grave significance of obesity and mental health on global welfare. The study underscores the burgeoning obesity crisis not just in Ireland, but worldwide, noting the staggering associated healthcare costs. It also highlights the heavy toll of mental health conditions, with the World Health Organization reporting a significant sliver of deaths owing to suicide, underlining depression's role in this grim statistic.

The study also considered previous research, suggesting that the relationship between obesity and mental health might be multifaceted. Lifestyle factors that we can typically control, like diet quality and physical activity, have been tied to both obesity and mental health. Chronic diseases, which are often linked to excess weight, can also trigger or worsen depression and decrease overall well-being.

The work fills a vital gap in knowledge, bringing attention to a connection that thrives across different lifestyle circumstances and illnesses. In light of the findings, the study puts forward a compelling call to action for public health initiatives to focus not just on the physical risks of obesity but also on the mental burdens it bears.


Lonergan C, Millar SR, Kabir Z (2024) Associations between adiposity measures and depression and well-being scores: A cross-sectional analysis of middle- to older-aged adults. PLOS ONE 19(3): e0299029.