4 Abstract The prevalence of obesity and its related cardiometabolic complications in children remains high across the world. Obesity is a multifactorial disease caused by interaction between genes and environmental factors. Genome-wide association studies have discovered several single nucleotide polymorphisms associated with obesity. A causal role of infection in the pathogenesis of obesity has also been considered, particularly the role of adenovirus 36 (Adv36). The aim of the Ph.D. thesis was to investigate the associations of obesity susceptibility loci (TMEM18, SH2B1, KCTD15, PCSK1, BDNF, SEC16B, MC4R, FTO) and Adv36 infection with obesity-related characteristics and complications in the Czech adolescent population. The results are described in eight publications, of which six are original papers and two are reviews. Studies were performed on a cohort of Czech adolescents recruited either from the general population (1,533 individuals from the epidemiological study) and from in-patient or outpatient weight management clinics (562 overweight/obese individuals underwent an intervention). The results demonstrated an association of TMEM18, SEC16B and FTO gene variants with obesity. Some variants of the genes involved in hypothalamic regulation of energy homeostasis − MC4R, BDNF, PCSK1 − were related to...

The term ‘epidemic’ is often used to describe the obesity phenomenon and indicate that overweight or obesity is a worldwide phenomenon. While the prevalence of overweight and obesity has been increasing, reviews on overweight and obesity studies indicate a clear need for further effectiveness studies of innovative and cost-effective strategies to improve the long-term outcomes of weight loss and weight maintenance programmes in large populations. Current weight loss interventions, while successful in the short term, are often not cost effective enough to deliver on a large scale because they are labour and time intensive. Most importantly, they do not cover large populations. Despite some individual successful weight loss in these interventions programmes, individuals still need to self- manage their weight following intervention. It is unrealistic to expect health professionals and clinicians to provide timely and long-term ongoing support for 2.1 billions overweight and obesity populations around the world (OECD Health Statics, 2014).Therefore, the solutions for weight control may be more effective if grounded within the online community, that is, design long-term solutions that build and draw on social capital to support weight maintenance and are scaled to cope with large populations. Understanding the individual weight loss experiences through informal online social support and utilising the advantages of computer-mediated communication (CMC) can be a timely and cost-effective way to help people self-manage their weight. A three-month online longitudinal phenomenological interview of 17 informants recruited from an online community forum was applied to explore the weight loss experiences with assistance of informal online social support. Four weight loss threads selected by the informants during their weight loss process were also interpreted to map out the key roles of informal online social support and the interaction process that takes place in an online community forum. This research describes the lived experiences of individuals’ self-help weight loss process and maps out the critical moments and differential experiences involved in the Stages of Change (SoC) to explain the individual differences during different weight loss stages. This research also identifies the interrelationships of Processes of Change (PoC) for facilitating behaviour change. The findings of this research contribute to demonstrate the interaction process between community members and the process of providing and receiving social support at different individual members’ weight loss stages, which helped them to continue to lose weight or maintain their weight. The informal online social support could meet different self-help weight loss individual’s needs during different weight loss stages, which is difficult to be provided by the healthcare providers. The findings also contribute to social marketing as a way of offering a cost-effective and efficient way to assist the self-help individual to self- manage their weight in the long term. It may also be a viable way of addressing the issues of costs and labour intensity found in the current weight loss interventions that want to serve large populations.

The primary purpose of this study was to evaluate the effects of a single bout of moderate-intensity exercise on acute (ad libitum lunch) post-exercise energy intake (PE-EI) and 12-hour energy intake in normal-weight and overweight sedentary males. Accuracy in estimating energy intake (EI) and energy expenditure (EE), solid vs. liquid carbohydrate intake, mood, and perceived hunger were also assessed. The study consisted of two conditions, exercise and rest, with each subject participating in each condition, in a counterbalanced-crossover design on two days. The participants were randomly assigned to either the exercise or resting (seated) control condition on the first day of the experiment, and then the condition was reversed on the second day. Exercise consisted of walking on a treadmill at moderate-intensity for 60 minutes. Eighty males, mean age 30+8 years were categorized into five groups according to weight status (overweight/normal-weight), dietary restraint status (high/low), and dieting status (yes/no). The main effects of condition and group, and the interaction were not significant for acute (lunch) or 12-hour PE-EI. Overall, participants estimated EE for exercise at 46% higher than actual exercise EE, and they estimated EE for rest by 45% lower than actual resting EE. Participants significantly underestimated EI at lunch on both the exercise and rest days by 43% and 44%, respectively. Participants with high restraint were significantly better at estimating EE on the exercise day, and better at estimating EI on the rest day. Mood, perceived hunger, and solid vs. liquid carbohydrate intake were not influenced by dietary restraint, weight, or dieting status. In conclusion, a single bout of moderate-intensity exercise did not influence PE-EI in sedentary males in reference to dietary restraint, weight, and dieting status. Results also suggested that among sedentary males, there is a general inability to accurately estimate calories for moderate-intensity physical activity and EI. Inaccurate estimates of EE and EI have the potential to influence how males manage their weight.

<p>Observational evidence links breakfast skipping, a behavior frequently observed among adolescents, with other poor health related behaviors that perpetuates a lifestyle associated with poor weight management and decreased cognitive performance. Furthermore, evidence suggests that both the consumption of breakfast and the quality of breakfast consumed may influence both weight and cognitive performance related outcomes. In an effort to improve the prevalence of breakfast consumption and the quality of breakfasts consumed among adolescents, recent initiatives have sought to increase participation in the federal School Breakfast Program (SBP). </p><p>The main objectives of this dissertation were to determine: 1) whether the habitual consumption of breakfast influences perceived appetite following the consumption of breakfast and whether habitual breakfast consumption influences post prandial appetitive sensations following the consumption of breakfasts varying in macronutrient distribution; 2) the feasibility of consuming an egg-based, ‘Breakfast in the Classroom’ (BIC) program in 8th grade students and whether the daily consumption of egg-based breakfasts improve School Breakfast Program participation, the quality of breakfasts consumed, and snacking behavior in 8th grade students; and 3) whether differences in cognitive performance exist between 6th-8th grade students who consume school breakfast, students who consume breakfast at home only, and students who skip breakfast following the initiation of a higher-protein Breakfast in the Classroom program. </p><p>This dissertation is organized into chapters that consist of published manuscripts or manuscripts formatted for submission to peer-reviewed journals. Chapter 2 consists of comprehensive review of the evidence linking breakfast consumption and composition to obesity and cognitive performance with an emphasis on the recent advances in school breakfast programs and future directions. Chapter 3 evaluates whether the habitual consumption of breakfast influences perceived appetite following the consumption of breakfast and whether habitual breakfast consumption influences postprandial appetitive sensations following the consumption of breakfasts varying in macronutrient distribution. Chapter 4 examines the feasibility of implementing an egg-based BIC program and subsequent effects on SBP participation, the quality of breakfasts consumed, and evening snacking in 8th grade students. Chapter 5 examines differences in cognitive performance between 6th-8th grade students who consume school breakfast, students who consume breakfast at home only, and students who skip breakfast following a higher-protein BIC. Chapter 6 summarizes the main findings and presents considerations for future research.</p><p>Collectively, the findings from this dissertation demonstrate:1) consuming 30 grams of protein at breakfast improves appetite and satiety compared to a breakfast containing 15 grams of protein, independent of habitual breakfast consumption in overweight adolescent females; 2) implementing a universally-free ‘Breakfast in the Classroom’ program that serves two additional eggs to a traditional school breakfast served via a traditional SBP is feasible and improves SBP participation, the quality of breakfast consumed, and reduces unhealthy evening snacking; and 3) students who consume breakfast at school, as part of a higher-protein BIC program, perform better on tasks assessing cognitive flexibility and executive function in middle school students when compared to students who skip breakfast, regardless of key behavioral and/or socioeconomic factors. Thus, this work suggests increasing protein content of school breakfasts using a universally-free distribution program is feasible and may provide benefits on overall diet quality and cognitive performance for 6th-8th grade students. <br></p>

Adolescent obesity is a growing health concern in the United States due to its increasing prevalence and comorbidities that can reduce longevity and increase morbidity. Advanced practice nurses (APNs) providing care in school-based health centers (SBHC) located in marginalized communities are uniquely positioned to work with adolescent students challenged with obesity. The management of adolescent obesity requires advanced skills and knowledge to promote healthy lifestyles, prevent obesity, and to directly address the many factors that contribute to the condition. The purpose of this project was to develop an education program for APNs to prepare them to work with students in prevention and control of adolescent obesity in the SBHC. The Shuler nurse practitioner practice model provided the framework to guide the project. A literature search yielded evidence-based care guidelines for adolescent obesity that were used to develop the education program. The program was provided to a panel of 5 clinical experts made up of 2 APNs and 3 pediatricians who work with adolescents who are obese. The panel evaluated the program using a 5-item, Likert-style questionnaire covering the 5 objectives of the program. Results ranged from a mean score of 3.4 to 4.0, indicating that the expert panel agreed or strongly agreed that the program met the objectives. This education program was provided to the SBHC administration and will be implemented in the next school term. The project may promote positive social change through increased APN knowledge of clinical practice guidelines for managing adolescent obesity and through improved adolescent health.

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L’objectif de recherche principal poursuivi dans cette thèse de doctorat est de mieux comprendre le rôle d’une insatisfaction corporelle dans l’adoption de pratiques de maintien et de changement du poids chez des adolescent(e)s québécois(es). Pour atteindre cet objectif de recherche principal, trois articles scientifiques liés les uns aux autres ont été rédigés. Chaque article poursuit des objectifs spécifiques (1er article: estimer les proportions d’adolescent(e)s québécois(e)s poursuivant un objectif de poids apparié et non-apparié à leur poids actuel et identifier les déterminants des objectifs de poids non-apparié au poids actuel, 2e article: identifier des associations entre un objectif de poids apparié vs. non-apparié au poids actuel et la fréquence d’utilisation de différents comportements liés au poids et à l’alimentation, 3e article: observer des associations entre différents degrés d’insatisfaction corporelle et l’utilisation de divers comportements liés au poids et à l’alimentation et examiner le rôle modérateur d’un objectif de poids apparié vs. non-apparié au poids actuel dans ces associations) permettant de répondre à l’objectif de recherche principal. Ces articles ont tous été élaborés à partir de l’analyse secondaire d’une banque de données quantitatives constituée par l’Institut de la statistique du Québec (ISQ) et nommée: Enquête sociale et de santé auprès des enfants et des adolescents québécois (ESSEA). L’ESSEA a été constitué auprès d’un échantillon populationnel et représentatif d’enfants et d’adolescent(e)s québécois(es) âgé(e)s de neuf, 13 et 16 ans. Les résultats de cette thèse indiquent qu’une insatisfaction corporelle est associée à la poursuite d’un objectif de poids non-apparié au poids actuel, ainsi qu’à l’utilisation de comportements liés au poids et à l’alimentation sains, malsains et déviants. Des associations ont également été observées entre l’objectif de poids poursuivi par un adolescent(e) et divers comportements utilisés pour l’atteindre. En effet, la poursuite d’un objectif de poids non-apparié au poids actuel est associée à l’utilisation de comportements malsains. Cette association n’est cependant pas présente en ce qui à trait à l’utilisation de comportements sains et déviants, ceux-ci étant strictement prédits par une insatisfaction corporelle. Des effets de médiation et de modération ont aussi été identifiés. Une insatisfaction corporelle est une variable de médiation entre une détresse psychologique chez les adolescentes et la poursuite d’un objectif de poids non-apparié au poids actuel. Finalement, un objectif de poids non-apparié au poids actuel est une variable modifiant l’association entre une insatisfaction corporelle et l’utilisation de comportements malsains chez les adolescent(e)s québécois(es). En conclusion, il existe diverses associations entre une insatisfaction corporelle et l’adoption de pratiques de maintien et de changement du poids chez des adolescent(e)s québécois(es). Une insatisfaction corporelle est donc une cible d’intervention pertinente pour la santé publique puisqu’elle peut servir de base à l’élaboration d’interventions visant la promotion d’un poids santé ainsi que de saines stratégies de contrôle du poids. / The main objective of this doctoral thesis is to better understand the role of body (dis)satisfaction in the adoption of practices directed toward body weight maintenance or body weight modification among Quebec adolescents. To reach this overall thesis objective, three theoretically and conceptually linked scientific papers were written. Although linked to one another, each paper pursues specific research objectives (1st article: to estimate proportions of adolescents with a weight goal that matched and mismatched weight status, and to identify correlates of a mismatched weight goal, 2nd article: to examine associations between matched vs. mismatched weight goals and the frequency of use of different weight-related behaviors, 3rd article: to examine associations between different levels of body dissatisfaction and different frequencies of use of weight-related behaviors and, to investigate whether or not the person’s weight goal moderates these associations) which allow for answering the main thesis objective. These papers were generated from secondary data analyses on a quantitative dataset built by the Institut de la statistique du Québec (ISQ) and named: Quebec Child and Adolescent Health and Social Survey. This dataset was based on data collected from a representative population-based sample of Quebec children and adolescents aged nine, 13, and 16 years old. The results of this thesis indicate that body dissatisfaction is associated with pursuing a mismatched weight goal as well as with the use of healthy, unhealthy, and disordered health behaviors. Associations are also observed between weight goals and weight-related behaviors used to reach weight goals. Indeed, pursuing a mismatched weight goal was found to be associated with the use of unhealthy weight-related behaviors across both sexes. This association is however not significant for the use of healthy and disordered health behaviors. These behaviors were solely predicted by body dissatisfaction. Mediation and moderation effects were also identified. It was found that being body dissatisfied mediated the association between psychological distress among adolescent girls and pursuing a mismatched weight goal. Finally, pursuing a mismatched weight goal was also found to moderate associations between body dissatisfaction and using unhealthy weight-related behaviors among both Quebec adolescent boys and girls. We conclude that there are various associations between body dissatisfaction and the adoption of practices directed toward body weight maintenance or body weight modification among Quebec adolescents. Body dissatisfaction thus represents a pertinent target for public health intervention in the sense that it can serve as the basis for the elaboration of interventions aimed at promoting healthy body weights and healthy weight management strategies.