Understanding the psychological basis of obesity

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The obesity epidemic is one of the largest public health crises of our time and every year more than 30,000 die young because of obesity. Compared to people with normal weight, people living with obesity experience a dramatically reduced quality of life, are far more likely to develop ill health and die younger. Obesity has been traditionally characterised using an 'organic' or biological model of disease: obesity is persistent because homeostatic systems defend against weight loss and the reason people with obesity die young is attributable to the biological strain of excess body fat. However, at present we lack a nuanced understanding of why obesity is so difficult to treat, why some people go on to develop more severe 'high risk' obesity and why obesity is associated with reduced life expectancy. Here we introduce and test a 'psychological burden' model of obesity, which proposes that the range of psychological factors associated with heavier body weight collectively are key to understanding obesity's persistence (why it is so difficult to lose weight and keep it off), progression (why some people progress to severe 'high risk' obesity) and the obesity-related disease burden (why obesity is predictive of ill health and early mortality). To test this, we first make use of large UK cohort studies (Millenium Cohort Study, National Child Development Study, British Cohort Study) to quantify the role that psychological factors collectively have in explaining (i) whether a person remains overweight/obese vs. returns to a healthier weight over the life course and ii) the development of severe obesity. We do so by examining how psychological factors collectively explain the tracking of obesity and the development of severe obesity across childhood and adulthood. Next, we exploit data from large-scale epidemiological studies (English Longitudinal Study of Ageing, US Health and Retirement Study) to examine how much of the obesity-related disease burden (i.e. declines in biomarkers of physical health, development of chronic health conditions and early mortality associated with obesity) is explained by the collective effect of the range of psychological factors associated with heavier body weight. This project moves beyond traditional approaches to understanding obesity that have either relied largely on biological accounts or studied a limited number of psychological factors in isolation. By understanding the collective effect that the psychological factors associated with heavier body weight have on obesity and obesity-related ill health, the present project has potential to change the way that the medical and public health community understand obesity and improve treatment approaches to reduce obesity and the obesity-related disease burden. There is currently a lack of psychological support in weight management interventions and services in the UK and a lack of consideration of the psychological basis of obesity in national government obesity strategy. Our project will highlight the psychological factors contributing to obesity outcomes and therefore has potential to inform policy. We will also be able to identify psychological factors that could be targeted in treatment efforts. To ensure this research is designed and disseminated in order to achieve long lasting impact outside of academia, we are partnering with the Obesity Health Alliance (OHA); a coalition of 44 organisations (including health charities, medical societies and campaign groups) that shape UK obesity policy by developing and advocating for evidence-based policy recommendations and influencing decision makers and the media. OHA members will provide input into final study designs to maximise likely impact and support us in ensuring that our findings are disseminated and communicated to key stakeholders and policy makers (e.g. UK Government Department of Health and Social Care, National Institute for Health and Care Excellence), where appropriate.