Howard, M; (2016) An examination of the influence of a fasted state on neurocognitive measures of impulsivity and compulsivity in healthy individuals: implications for eating disorders research. Doctoral thesis , UCL (University College London).

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Abstract

Neurocognitive research into eating disorders has suggested that Anorexia Nervosa (AN) has a ‘compulsive’ profile, characterised by features such as poor cognitive flexibility. Conversely, Bulimia Nervosa (BN) has been linked to increased impulsivity. Chapter 1 systematically examines the literature to show both AN and BN can be conceptualised as sharing elements of impulsivity and compulsivity. The review identified the existing research as inconsistent and inconclusive. Chapter 2 begins to address the question of whether differences in the metabolic state of the participants could account for this inconsistency. Individuals with BN, compared to HCs undergo periods of short-term fasting, and although individuals with BN are matched to Healthy Controls (HCs) for body max index, there is no current marker of fasting. The study reported in Chapter 2 showed that in HCs, 20 hours of fasting significantly alters the expression of impulsivity on two of four neurocognitive measures. Chapter 3 builds on this to investigate compulsivity using the same paradigm, but did not show any influence of fasted state on performance. Chapter 4 describes two studies investigating the relationship between hunger, impulsivity and compulsivity, respectively. The results of Chapter 4 indicated an association between hunger and increased reflection impulsivity, but no link between hunger and other measures of impulsivity, compulsivity or central coherence. Chapter 5 investigates whether the effect of fasting observed in Chapter 2 can be attributed to the types of cues used during these tasks. The study examined whether changes to the physiological state of the individual increases the rewarding and motivational value of food. Results indicate that short-term fasting increased the rewarding value, salience, and interference from food stimuli. Selfreported cravings together with impulsivity independently predicted amount eaten when fasted. Chapter 6 summarizes these findings, the relevance to the fields of eating disorders, limitations and implications for future research.

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