Impulsivity and eating behaviour: an examination of subtypes of impulsive behaviour and overeating in healthy females

A wealth of support has shown higher levels of state and trait impulsivity can be found among those individuals prone to developing problematic eating behaviors and obesity. Thus, upon commencing the investigations in this thesis, it was hypothesized that impulsivity is an individual difference implicated in overeating behaviour. Increasing information indicates that there are divisions within impulsivity subtypes. Prior to this thesis, studies in the field of eating behaviour had not distinguished between subtypes of impulsivity. This was problematic because it limited researchers ability to describe how impulsivity is specifically involved in the perpetuation of overeating behaviour. The purpose of this Thesis was to provide a methodical inquiry into the relationship between impulsivity, and its relation with overeating behaviour. This objective was achieved by separating three prioritites, first to determine if impulsivity was higher in women who self report overeating, second to define differences between impulsivity classifications and determine if there was a consistnent pattern between self reported overeating and a relation to a subtype of overeating behaviour, and third to designate a specific impulsivity subtype to individuals who self report overeating behaviour. Six Experimental Chapters explored these three priorities. Two exploratory correlational/regression analysis were used to refine our ability to operationalize measures of self reported overeating and impulsivity (Chapters 2 and 5). Chapter 3 and Chapter 5 were devoted to assess the impact that ingestion of palatable food, and the violation of cognitive boundaries of restraint, have on subsequent impulsivity. The two remaining investigations were structured to assess the impact that environmental factors have on impulsive behaviour. In Chapter 4, a Controlled versus Unrestricted eating environment were manipulated to determine whether overeaters benefit from a structured breakfast meal prior to completing a battery of impulsivity tasks. In Chapter 7, anticipation for a rewarding food item was manipulated in two conditions. In this final Chapter, the impact that anticipation for rewarding food in self reported overeaters was assessed. The battery of impulsivity tasks in this thesis include the Balloon Analogue Risk Task (BART), The Go No Go task, the Matching Familiar Figures task (MFFT), and two versions of the Delay Discounting Task (DDT). Impulsivity was classified along a spectrum of Reward Reactivity versus Inhibition subtypes, based on Evenden´s (1999) classification of impulsive behaviour. Participants tendency to overeat was based on a dual classification of tendency to restrain eating (Three Factor Eating Questionnaire- Restraint) with tendency to overeat (Three Factor Eating Questionnaire-Disinhibition subscale). The outcomes of the five experimental investigations in this thesis demonstrated a reliable pattern by which participants with high Disinhibition scores had significantly more impulsive responses on the MFFT task. These results indicated that inhibition impulsivity is the clearest individual difference to be found between healthy volunteers who self-report overeating. The role that Inhibition Impulsivity plays in the perpetuation of overeating behaviour is illustrated and discussed in each Experimental Chapter.