Between-meal snacking in daily life

Worldwide, the number of people with overweight and obesity has increased substanti allyin recent decades. Overweight and obesity are prominent risk factors for health problems such as type 2 diabetes mellitus, cardiovascular diseases, certain types of cancer, andosteoarthritis. Energy intake, in particular snack intake, has often been identified as the driving force of the rapid increase in overweight individuals. Research into dietary behavior has mainly focused on the role of cognitions in predicting dietary intake. Socio-cognitive models, such as the Theory of Planned Behavior (TPB) have been used in explaining why people may adopt healthy behavior or why they fail to do so. From the perspective of dual system models, however, research has demonstrated that snacking behavior may either be guided by reflective processes such as attitudes or intentions, which is in accordance with the socio-cognitive models of behavior, or by impulsive processes which originate from factors such as habits or fleeting emotions (i.e.positive and negative affective states). As such, it is conceivable that impulsive processes contribute uniquely to explaining variance in dietary behavior. To be able to associate dynamic psychological processes such as affective states with between-meal snack intake it is important to repetitively measure moment-to-moment snack intake and affective states in the context of daily life. Therefore, for the purpose of this research project,Snackimpuls, a smartphone application based on ESM, was developed to gain insight into the determinants of between-meal snacking and their dynamic interplay in daily life.This dissertation was divided into three parts. The aim of the first part was to compare moment-to-moment energy intake from self-reported snacks as measured by the signal contingent Snackimpuls app, with the measurements of a traditional event-contingent paper and pencil estimated diet diary. The second part of this dissertation consisted of two studies that aimed to provide insight into the role of habit (chapter 3) and affect(chapter 4) on momentary energy intake from daily life snacks. The aim of the third part of this dissertation (chapter 5) was to further elucidate the complex relationship between minor stressful daily events, between-meal snacking (yes/no) and its macronutritional components, and negative affect.Chapter 1 provides a general introduction of the background and theoretical perspectives of the main study presented in this dissertation. In accordance with the dual system perspective, this chapter highlights the need for research towards the role of habit and affect in predicting energy intake from snacks in real life settings. Furthermore, the need to extend our knowledge on the impact of snacking and its nutritional components on negative affective stress reactivity is discussed. Finally, the added value of ecological momentary assessment is addressed. Chapter 2 of this dissertation compares moment-to-moment energy intake fromself-reported snacks as measured by the signal-contingent Snackimpuls app, with the measurements of a traditional event-contingent paper and pencil estimated diet diary. This chapter shows that both instruments were comparable in assessing moment-to-moment energy intake from snacks (kcals). Research purposes will largely determine the most appropriate sampling procedure (i.e. signal-contingent or event-contingent) of choice. Chapter 3 provides insight into the association between habit and energy intake from snacks in daily life. This chapter shows that habit strength was significantly associated with moment-to-moment energy intake from between-meal snacks: the higher the strength of habit to snack between meals, the higher the amount of momentary energy intake from snacks. With respect to demographic individual differences, additional analyses showed that this association only applied to individuals with a low to middle level of education. It is recommended to address habitual between-meal snacking in future interventions targeting low to middle educated individuals. Chapter 4 provides insight into the association between affective states (positive and negative affect) and energy intake from snacks. This study shows a significant negative main effect of momentary NA on moment-to-moment energy intake. The higher momentary NA, the lower the subsequent amount of kilocalories consumed. Interaction analyses,show that men decreased their energy intake after experiencing NA. No associations were found in women, nor in the other demographic groups. With regard to PA, this study shows no main effect. Interaction analyses, however, show that men and young adults (20-30) increased their intake after experiencing PA. No associations were found in women nor in the other age groups. Future interventions aiming at reducing energy intake might consider addressing PA-related snacking in young adults and men. Chapter 5 provides insight into whether or not momentary snacking (yes/no) could actually moderate (i.e. dampen) the association between momentary stress and subsequent NA (i.e. negative affective stress reactivity). And, if so, whether this moderating effect can be replicated by the macronutrient intake (i.e. carbohydrates (grams), fat (grams), and protein (grams)). This study revealed a slight dampening effect of snacking on negative affective stress reactivity, meaning that when individuals have snacked in response to daily hassles, subsequent NA is slightly lower compared to when individuals did not snack. However, this study also showed that this dampening effect of snacking on stress reactivity, could not be replicated by its macronutritional components (i.e. carbohydrates, fat, and protein). On the contrary, the amount of carbohydrates consumed showed an enhancing effect on negative affective stress reactivity (i.e. the higher the carbohydrate intake since the previous beep, the higher momentary NA in response to momentary stress). No moderating effects were found for fat and protein. These findings provide ground for further investigation towards the decisive mechanisms in the stress dampening role of snacking. Finally, Chapter 6 provides a general discussion. In this chapter the findings of this dissertation are summarized and integrated, methodological issues are discussed, and reflections are made on implications for future research and practice. The most important strengths of the main study are the large study population and the high number of momentary reports. The chapter concludes that habit strength and positive affect contribute to an increase in energy intake in low to middle educated individuals (habit), and in young adults and men (positive affect). Based on our findings it is argued that investigating snacking behavior in additional ways than proposed by socio-cognitive models is of importance. Our findings with regard to habit strength and affect seem to endorse the relevance of both reflective and impulsive processess as proposed by dual system models. It is recommended that behavioral change interventions towards healthy dietary behavior, which are often directed towards cognitive determinants, also target impulsive processes such as unhealthy dietary habits and positive affect-related snacking. The last part of this dissertation shows that although snacking does alleviate negative affective stress reactivity, this effect cannot be attributed to its macronutritional components. These findings provide ground for further investigation towards the decisive mechanisms in the stress dampening role of snacking.