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Understanding the psychological legacy of past obesity

Researchers from the University of Liverpool, in collaboration with researchers in the UK, Ireland, and North America, have led a study to better understand the potential long-term consequences of previous obesity. In a recently published paper, the University of Liverpool team found that obesity may be psychologically scarring and is also linked to increased risk of mortality independently of current weight.

Figure 1: Diagram of the study design. For both NHANES and HRS, psychological outcomes and sociodemographic covariates at baseline were examined. In HRS, a measure of depressive symptoms was available in every wave, and therefore, pre-baseline depressive symptoms prior to when obesity developed were controlled to estimate the effect of past obesity on current (baseline) depressive symptoms. Credit: BMC Medicine (2023). DOI: 10.1186/s12916-023-03148-3

The global prevalence of obesity has nearly tripled in the last four decades (1975–2016) and is now a major public health crisis. Using a sample size of more than 40,000 participants from two nationally representative studies, the new research offers new insights into the potential long-term impacts of obesity on mental health and life expectancy.

Data were from the National Health and Nutrition Examination Survey (NHANES) (n=29,047) and the Health and Retirement Study (HRS) (n=11,998). Past obesity was defined based on maximum lifetime weight in NHANES and the highest weight from past study waves in the HRS. Across both studies, current depressive symptoms were analysed (Figure 1). A set of ten additional well-being measures were combined to produce an ‘index of impaired well-being’ in HRS. Subsequent all-cause mortality was examined using National Deaths Index records in NHANES and household interviews in HRS. Linear or logistic regression, Cox proportional hazard regression, and causal mediation models were used.

They found that past obesity was associated with greater current depressive symptoms after controlling for current weight status and in analyses limited to those who were no longer classified as having obesity in NHANES (β = 0.17; 95% CI: 0.13, 0.22) and HRS (β = 0.20; 95% CI: 0.08, 0.31). In HRS, past obesity was also associated with a range of current negative psychological outcomes, including an index of impaired psychological well-being (β = 0.16; 95% CI: 0.05, 0.27). Past obesity was also associated with a higher risk of early mortality in both NHANES and HRS (HR = 1.31; 95% CI: 1.16, 1.48 and HR = 1.34; 95% CI: 1.20, 1.50, respectively). Depressive symptoms explained 6% (95% CI: 0.01, 0.10) and 5% (95% CI: 0.01, 0.09) of the association between past obesity and premature mortality in NHANES and HRS, respectively. Impaired psychological well-being partly mediated the association between past obesity and premature mortality by 10% (95% CI: 0.04, 0.16) in HRS.

Dr I Gusti Ngurah Edi Putra and Professor Eric Robinson from the University of Liverpool, worked with Dr Michael Daly, Maynooth University, Professor Angelina Sutin, Florida State University, and Professor Andrew Steptoe, University College London, for the study. Their findings suggests that previous periods of living with obesity may be associated with long-term 'scarring' consequences on mental health, and there may be a psychological legacy of obesity even among people who previously had obesity but do not anymore.

"This paper offers valuable insight into the potential long-term psychological impact on those who have experienced obesity during their lives,” explained Putra from the Institute of Population Health. “Given the increased number of people who are developing obesity at early ages and people actively attempting to lose weight, a history of obesity is now more common, and the findings of the present study suggest this history of obesity may be associated with the development and/or persistence of depressive symptoms and impaired well-being. Our findings suggest that the psychological burden of obesity may be larger and have longer-term consequences than previously assumed."

The findings were reported in the paper, ‘The psychological legacy of past obesity and early mortality: evidence from two longitudinal studies’, published in BMC Medicine.


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