An investigation of the addictive nature of food

The thesis commences with a literature review suggesting common neural circuits mediate food and drug rewards and discusses the application of behavioural and biological theories of addiction to overeating and obesity. Research exploring the relationship between food, reward and overeating is lacking. The current dominant neurobiological theory suggests reward can be separated into psychological components; ‘wanting’ (incentive salience attribution) and ‘liking’ (pleasurable/aversive evaluation) mediated by separate neural substrates. Features of overeating and addiction are discussed with the conclusion that there are many similarities. However, presence of tolerance and withdrawal effects, considered central to drug addiction, is weaker in overeating. Psychological processes of restraint, ambivalence and attribution appear to be more applicable to overeating. Although some authors maintain that labelling overeating as an addiction risks trivialising serious addictions, it is argued that the characterisation of overeating as an addiction is important as both issues are associated with serious health complications. The empirical study investigated if participants who were overweight showed an enhanced attentional or approach bias for food-related stimuli compared to participants of a healthy weight. The relationships between weight, attentional bias and implicit and explicit measures of stimulus valence were explored. Present findings suggest individuals who are overweight have reduced attentional bias for food cues compared with people of a healthy weight. Evidence of an over-responsive reward system (over-active dopamine system) in response to the sight of food was not present in participants who were overweight. Further research is needed to clarify the issue.