Psychometric and behavioural examination of the validity of “food addiction” in the general population

Background: Some people attribute the failure to control their consumption of frequently consumed, often highly palatable foods to ‘Food Addiction’ (FA), but the scientific validity and utility of this term is disputed. In 2009, a tool was developed in an attempt to diagnose and measure the severity of so-called FA: the Yale Food Addiction Scale (YFAS), which has formed the cornerstone of the human experimental literature on FA. This thesis aims to examine the psychometric construct of FA and the YFAS through: a systematic literature review (Chapter 2); examining the psychometric properties of the YFAS using factor analysis (Chapter 3) and a comparison with a widely-used measure of trait binge eating (Chapter 4) and; exploring the role of YFAS scores on food perceptions (Chapter 5), and homeostatic (Chapter 6) and hedonic (Chapter 7) control of appetite. Results: Much of the literature on FA made the assumption that food addiction is a valid diagnosable condition. However, this interpretation was based on very limited data (Chapter 2) and a tool with weak psychometric properties (Chapter 3) which was not able to distinguish behavioural characteristics from those identified by the Binge Eating Scale (BES; Chapter 4). High fat and energy dense foods were perceived as most associated with ‘problematic eating behaviours’ and ‘addictive potential’, though these perceptions were not related to YFAS scores (Chapter 5). Higher YFAS scores were associated with lower habitual physical activity, but no impairment to homeostatic control of food intake (Chapter 6), though high YFAS scorers demonstrated greater energy and fat intake, along with a preference for high fat sweet foods and snacks (Chapter 7). Conclusion: It was concluded that FA appears synonymous with strong preferences towards highly palatable foods, especially high fat, sweet snacks. The work in the thesis found no strong evidence that food addiction (as measured by the YFAS) is associated with ‘addictive’ food behaviour or obesity. Research and debate surrounding the YFAS may divert attention and resources away from identifying and addressing the psychobiological determinants of overeating.