Effects of sleep deprivation on eating behaviour in a sample of individuals reporting binge eating symptoms: a quasi-experimental study

Epidemiological studies reported an association between poor sleep and increased food intake and obesity at different ages. Emerging evidence (both cross-sectional and longitudinal) have shown that sleep quantity/quality and eating behaviour are strictly linked, and different underlying mechanisms may mediate or moderate this relationship (e.g. cognitive and emotional mechanisms). Moreover, experimental studies found that partial and acute sleep deprivation may increase food intake and may impair executive and emotional functioning. The quasi-experimental study presented in this PhD dissertation aimed to evaluate the effect of a night of partial sleep deprivation (5 hours of sleep allowed) on food intake, executive functions and food craving compared to a night of habitual sleep. The potential mediating effect of executive functions (backward inhibition) and food craving (lack of control) and the potential moderating effect of emotional eating and depression were also taken into account. The sample consisted of participants reporting binge eating symptoms (Binge Eating Group) and self-defined healthy control participants (Control Group). After an initial screening, both groups were invited to the laboratory after a night of habitual sleep and after a night of partial sleep deprivation, in a counterbalanced order. At their arrival in the lab, after both nights, they completed different computer tasks to assess executive functions and craving, valence and arousal for high palatable food images. They were then invited to have breakfast in the lab, in which food intake was unobtrusively measured. Participants were also asked to monitor their sleep through an electronic portable device and sleep diaries. Food intake over the course of the day was also assessed using food diaries. This complex study provides novel empirical evidence on the relationship between poor sleep and eating behaviour and the underlying mechanisms that could mediate or moderate this relationship. Indeed, it took into account many aspects of eating related behaviours, emotions and cognitions. The present dissertation includes two parts. The first part presents the theoretical background on which is based the empirical contribution presented in the second part. The literature addressed in the first part aims to support the choice of the variables (independent, dependent, mediators and moderators) that were considered in the study and the hypotheses advanced. First, it presents the state of art on the link between poor sleep and obesity at different ages; then, the link between poor sleep and diet pattern and the results of experimental studies on the effect of sleep deprivation on food intake are discussed. Furthermore, it discusses the role of potential factors influencing this relationship such as biological (e.g. appetitive hormone disruption), cognitive (e.g. impaired executive functions), and emotional processes (e.g. emotional eating, negative affectivity). The first part also addresses the relation between poor sleep and eating disorders in order to explain why a sample of people reporting binge eating was selected for studying the link between poor sleep and eating behavior. The second part presents a study conducted for testing different hypotheses related to the relationship between sleep and eating behavior. Although the study is one, for sake of clarity it is split into different chapters according to the specific hypotheses tested and the specific outcomes addressed. The first chapter presents the design and the general aims of the study, explains the methodology applied (self-report instruments and objective measures employed in the selection, screening phase and sleep assessment) and describes the procedure of the study and the statistical analyses plan.. It also includes the descriptive results on groups characteristics and results of the sleep manipulation check, as well as a brief discussion of these results. All the following chapters have a similar organization: they briefly summarize the relevant theoretical background on which the specific hypotheses tested were based, then they describe the specific methodology and instruments employed for measuring the variables and the relationships tested, the statistical analyses, the results and the discussion. Thus, the second chapter focuses on food intake taking into account the potential moderating role of emotional eating; the third discusses the results on executive functions and its potential mediating role in affecting food intake. The fourth focuses on food craving and its potential role as mediator in increasing food intake. Finally, taking together the results presented in the empirical chapters, a general discussion and a conclusion are formulated, highlighting the clinical implication and the possible future directions.