The aim of this thesis was to advance the methods of assessing laboratory based running performance and study the influence of carbohydrate-electrolyte( CHO-E) solutionso n self-selectedr unning speeds. The first study (Chapter 4) attempted to improve the methods used for treadmill timetrials by using an automated treadmill system that allows runners to rapidly change their running speed without engaging with the treadmill control panel. To this end, the study examined the repeatability of a1h running time-trial, in which the aim was to achieve the greatest distance in the set time. The coefficient of variation (CV), estimated using ANOVA with subject and trial as main effects, was 1.4%. Therefore, it was concluded that asking runners to cover as much distance as possible in 1 h, using an automated treadmill system is a reliable method of assessing endurance performance in endurance trained runners...

A growing body of evidence suggests that athletes are at increased risk of disordered eating and eating disorders. The principal explanation proffers that extreme pressure to lose weight for performance gains can encourage the development of pathological attitudes and behaviours with regards to food and weight. The current consensus is that elite female athletes participating in sports with a focus on leanness or aesthetics are at greatest risk. This existing knowledge has emerged from a literature base characterised by a narrow focus on prevalence rates and risk factor identification. As a consequence, there are few examples of studies that address disordered eating in sport interpretively and we know little about how athletes experience the illness. The overarching aim of this thesis therefore, was to interpretively explore athletes subjective accounts of their disordered eating experiences, adding new, alternative insights that compliment the existing literature. In Study 1 I adopted an interpretative phenomenological analysis as a means to give voice to four athletes who have experienced disordered eating. The aim of this study was to document athletes personal accounts and to interpret these accounts from a psychological perspective. In-depth, semi-structured interviews were conducted and verbatim transcripts were analysed according to the procedures of IPA. Three superordinate themes emerged from the data: the struggle to disclose, social support needs, and identity challenges. Athletes stories provided rich descriptions of their subjective disordered eating experiences. Their accounts give critical insight into the impact of eating disturbance on the lives of athletes. In Study 2 I drew on narrative theory to interpretively analyse the life-story of Holly, a female athlete who engages in severe self-starvation. The broad aim here was to build on the interpretive insights gleaned in Study 1 and provide a detailed, qualitative exemplar of an athlete s life with disordered eating. More specifically, this study sought to explore the narrative processes by which an athlete comes to understand disordered eating and the impact this holds for experience. More than 7 hours of life history data was gathered over a period of 8 months through unstructured interviews. Holly described a struggle to align her life experiences with a culturally specified achievement narrative that lauds normative success. When neither her academic nor sporting endeavours fulfilled the achievement narrative, Holly was thrust into emotional turmoil and began to conceive of self-starvation as a means to achieve. Holly s narrative is in many ways fractured and void of the coherence necessary to move on from her troubles. It is argued that narrative realignment and coherence might be encouraged through narrative therapy. For Study 3, I sought to add a further detailed exemplar to the disordered eating in sport research base. Again building on the initial insights of Study 1, extended life-history data provided scope to delve into the deep complexities and pertinent ambiguities that characterise lived experiences. In applying principles of narrative analysis to this data, the objective was to provide further details as to how a disordered eating athlete makes sense of illness and the implications of this meaning making for future experiences. To achieve this I explored the stories of Beth, a former elite athlete with experience of anorexia nervosa and, as she revealed, sexual abuse. Six unstructured life history interviews took place over a period of 12 months yielding more than 9 hours of interview data. Due to a lack of previous narrative opportunities, the story Beth told was in many ways embryonic. Throughout our conversations Beth constructed multiple, fragile and sometimes contrasting narrative coherences indicative of a fragmented and uncertain understanding of her life. Beth s atypical story helps create a more complete understanding of eating disorders in sport and serves as an additional narrative resource from which others might draw to story experience. With Study 4 I sought to address the lack of family involvement in disordered eating in sport research. Given it is widely accepted that families are important in the management and treatment of eating disorders, I explore the experiences of an elite athlete with an eating disorder as well as the experiences of her parents. The underlying aim here was to explore the impact of athlete disordered eating on participants, both individually and as a family. Family members attended interviews individually on 3 separate occasions over the course of a year. Analysis involved repeated readings of the transcripts, sensitising towards issues of narrative content and structure. Participants interpreted the eating disorder through specific narrative types which shaped their experiences and guided their actions. Difficulties arose when personal experiences strayed from the preferred narrative to live by and when family members held contrasting narrative preferences. Suggestions are forwarded as to how an appreciation of eating disorder illness narratives might inform treatment and support practices. In conclusion, this thesis has demonstrated that it is insufficient to study disordered eating through solely positivist means. It is only through consistent, focused, interpretive study that a fuller, more complete, understanding of the illness can be achieved. Specifically, we must begin to add experiential insights to the medical preoccupation with nosology and symptomatology. This thesis has taken a significant step towards adding such insights. When invited to recount their experiences, athletes provide rich, powerful, subjective accounts that enable us to see disordered eating in sport through a new lens. The way athletes make sense of illness is sometimes ambiguous and contradictory, often complex and transient and always consequential for future experiences. Essentially, the narratives used to describe disordered eating impact on how disordered eating is lived through. As such, future research must explore the potential of narrative therapy to ease future disordered eating experiences, while also continuing to add to the critical mass of interpretive studies available.

The nutrition transition is recognised as a change in dietary pattern from a low fat, high fibre diet to a high fat, high energy, low fibre diet. This change has been accompanied by an increase in nutrition related non-communicable diseases (NCDs) such as obesity, non-insulin dependant diabetes mellitus (NIDDM), and cardio-vascular disease (CVD). The impact on health is a rising concern because these NCDs are not confined to adults but are also being increasingly observed in children and adolescents in developing countries. The nutrition transition is driven by changing socio-economic conditions, food technology, distribution and marketing systems, and urbanization. The evidence on which the nutrition transition is based comes mostly from national aggregate data on adult samples and there is a dearth of information about the aetiology and characteristics of nutrition transition at a group or individual level in adolescents. The aim of this study is to investigate the dietary intake and body composition outcomes, in a sample of South African urban adolescents in the context of the nutrition transition. These adolescents have been followed from birth within the Birth to Twenty birth cohort set in Soweto and Johannesburg. A pilot study was conducted to assess the quantitative food frequency questionnaire (FFQ) which was to be administered to measure usual dietary intake. Consequently, the FFQ was modified according to the findings from the pilot study. The modified FFQ was administered to a sample of 15-year-old adolescents (n=154) and demographic factors, physical activity, pubertal development, socioeconomic status (SES) and body composition were measured using routine cohort standard protocols. Bivariate and multivariate analyses were performed to investigate the associations of these 'factors with dietary intake (total energy intake (kcal), % fat, carbohydrate, sugar and protein intake) and body composition (body mass index, relative % fat and lean mass). The macronutrient intake of the urban adolescent sample was 33.3% fat,51.8% carbohydrate, 10.7% protein and 14% added sugar as a proportion of total energy intake. The macronutrient composition of the current diet and the most commonly consumed foods suggests a transition towards the diet consumed by transitioned societies with a greater transition in the added sugar intakes. There were no significant predictors of energy intake in the linear regression analysis. No significant associations were observed between socioeconomic status (SES) and energy intake, % fat, carbohydrate or added sugar intake. However, SES was positively associated with % protein intake. Significant differences (p=O.015) in the prevalence of overweight and obesity between girls (24.7%) and boys (9.7%) were observed. The odds of being overweight or obese increased if the participant was female, had high SES and mature breast/genitalia development. None of the dietary intake variables had a significant association with the body composition outcomes. A transition towards a typical 'western 'diet is evident suggesting that this sample of adolescents have a similar dietary risk for NCDs to their counterparts in transitioned societies. Possible intervention strategies are suggested in the light of the findings from this study.

Previous research has shown that over time, humans can develop learnt associations between the sensory profile of a food and the energy it contains. These associations are then used to guide appetite for the same food in future situations. However, whether more acute, explicit information relating to the nutritional content of food can also shape eating behaviours in non-dieting individuals remains undecided. Following a review of previous literature, several methodological questions were raised relating to the effectiveness and validity of experimental manipulations used in some previous studies. The main aim of this thesis is to re-assess whether nutritional information could influence eating behaviours when these factors have been taken into consideration. In two initial experiments designed to address these issues, an interesting association was observed between participants' initial expectations of a preload and their ability to compensate for covert manipulations of its energy content. In order to further investigate this association, measures were developed based upon psychophysical analysis to provide an alternative method of measuring expectancies of the satiating efficacy of a food. The use of this measure allowed a quantifiable measurement of a participant's expectancies towards a food, while lessening the risk that demand effects were contaminating results. The final experiments of this thesis then re-examined the earlier observation that expectations of foods could mediate the regulatory responses that ingesting the food creates. The observed results did not support the proposal that expectancies of a preload were mediating compensatory ability by prompting attention towards visceral cues. Instead, results suggested that enhanced compensation was observed when participants were provided with an unexpected deficit in energy intake, rather than an unexpected surplus. This introduces the concept that an individual's short-term compensatory ability may be partly determined by pre-existing expectations about the food they are eating. The implications of this finding with regard to dietary preloading paradigms are discussed, and the possibility that this mechanism could explain the poor compensatory ability often associated with liquid loads is explored.

The increasing evidence of associations between inactivity and poor diets in young people and both immediate and long term health implications is of public health concern. There is a need to further understanding of young people's health behaviours, to facilitate the development of behaviour change strategies promoting healthy behaviours. This thesis, provides seven studies focusing on the family environment and the influences that the family and parents have on young people's physical activity and dietary behaviours. Chapter 2.1 describes a systematic review of family correlates of fruit and vegetable consumption in children and adolescents. Chapter 2.2 describes a systematic review of family correlates of breakfast consumption among children and adolescents. Systematic reviews are an essential component of evidence-based practice, and both reviews were conducted to examine the state of the current literature examining family environmental influences on aspects of young people's dietary behaviours. In the context of this thesis, these systematic reviews are of primary importance as they were instrumental in shaping and informing the direction of the research described in later chapters. Chapter 3 broadens the investigation of young people's health behaviours and describes two cross-sectional studies examining both physical activity and dietary behaviours. Chapter 3.1 describes a study examining patterns of adolescent physical activity and dietary behaviours. This study describes how adolescents are at risk of not meeting the recommendations for multiple health behaviours (e.g. physical activity, fruit and vegetable consumption, and breakfast consumption). Chapter 3.2 was designed to fill several gaps in the literature about the correlates of multiple health behaviours and also to gain a greater insight into the transferability of parental behaviours to different health behaviours in children. Chapter 3.2 describes a study examining family influences on young peoples fruit and vegetable consumption and physical activity, and on combinations of these behaviours (e.g. high physical activity and low fruit and vegetable consumption). Chapter 4.1 was designed to fill gaps in the literature by examining the association between family circumstance (parental marital status, maternal education, maternal employment status, number of brothers and number of sisters) and adolescent dietary behaviour, and 2-year change in dietary behaviour. Chapter 4.2 was designed to fill gaps in the literature by examining the relationship between parenting styles, family structure and aspects of adolescent dietary behaviour. Together, the six studies described above established a rationale and informed the content of the pilot family-based intervention described in Chapter 5. This thesis found that particular aspects of the family environment and particular attributes of parenting were associated with positive physical activity and dietary behaviours of young people. Such findings add considerably to the existing literature and are important as they suggest that even as young people age, the family environment and the emotional context within which parent-child interactions occur are vital for positive health behaviours. Targeting such facets of the family and parenting holds great potential for behaviour change strategies.

Selenium is a micronutrient essential for human health. Low Se intake versus Se supplementation have been reported to elevate and lower mortality from colorectal cancer. Se is present in selenoproteins including glutathione peroxidases (GPx) 1-4. GPxs are antioxidant enzymes that protect cells from excessive oxidative stress and they may have a role in maintaining innate immunity homeostasis against inflammatory stimulation from exposure to luminal bacteria. This thesis describes studies of the regulatory effects of Se depletion and selenoprotein knockdown in the gastrointestinal cell line Caco-2 in relation to inflammatory responses. A luciferase reporter model was developed in which Caco-2 cells were stably transfected with gene constructs in which luciferase expression was under the control of regulatory elements that bind the Nuclear Factor-kappa B (NF B), a transcription factor central to inflammatory signaling pathways (Chapter 3). As a control reporter luciferase coding sequences were linked to a TATA box. When Caco-2 cells expressing these constructs were grown in Se-deficient conditions, a 30% increase of reporter activity and a 50% increase in endogenous interleukin 8 mRNA levels were observed after stimulation with TNF . In comparison, no changes in reporter activity were found in Se-deficient cells after stimulation with flagellin (Chapter 4). Small interfering RNA was used to knockdown expression of individual selenoproteins including GPx1, GPx4, SelW and SelH (Chapter 5). Knockdown of GPx1 expression by ~55% led to a 25% decrease of reporter activity and a 17% decrease of IL8 mRNA level after stimulation with TNF ✁ . Knockdown of SelW or SelH expression had no observable effect on reporter activity. In addition, Se depletion elevated cellular ROS production as assessed by Carboxy-2’7’-dichlorodihydrofluorescein diacetate staining whereas GPx1 knockdown had no significant effect (Chapter 5). Knockdown of GPx4 by 85%, as assessed by RT-PCR and Western blotting, had little effect on TNF -driven luciferase activity. However, GPx4 knockdown lowered flagellin-induced reporter activity by 20% and interleukin 8 mRNA levels by 40% (Chapter 6). It is concluded that 1] low Se supply affects NF B inflammatory response in Caco-2 cells, 2] the exact role of different selenoproteins in this effect remains to be elucidated, and 3] the endogenous and exogenous inflammatory responses in Caco-2 cells are differentially regulated by Se supply and by antioxidant selenoproteins.

Orlistat is an anti-obesity treatment with which several gastrointestinal (GI) side-effects are commonly associated in the initial stages of therapy. There is no physiological explanation as to why two-thirds of those who take the drug experience one or more side-effects. It has been hypothesized that the GI microbiota may protect from or contribute to these GI disturbances. Using in vitro batch culture and human gut model systems, studies were conducted to determine whether increased availability of dietary lipids and/or orlistat affect the composition and/or activity of the faecal microbiota. Results from 24-h batch culture fermentation experiments demonstrated no effect of orlistat in the presence or absence of a dietary lipid (olive oil) on the composition of bacterial communities [as determined by fluorescence in situ hybridization (FISH) and denaturing gradient gel electrophoresis (DGGE) analyses], but did show there was great variability in the lipolytic activities of the microbiotas of individuals, as determined by gas chromatography analysis of long-chain fatty acids in samples. Subsequent studies focused on the effect of orlistat in the presence and absence of lipid in in vitro human gut model systems. Systems were run for 14 days with gut model medium (GMM) only (to steady state, SS), then fed at 12-h intervals with 50 mg orlistat, 2 g olive oil or a mixture of both for 14 days. FISH and DGGE were used to monitor changes in bacterial populations. Bacteria were cultivated from the GMM only (control) systems at SS. All strains isolated were screened for lipolytic activity using tributyrin agar. FISH and DGGE demonstrated that none of the compounds (singly or in combination) added to the systems had any notable effect on microbial population dynamics for any of the donors, although Subdoligranulum populations appeared to be inhibited by orlistat in the presence or absence of lipid. Orlistat had little or no effect on the metabolism of indigenous and added lipids in the fermentation systems, but there was great variability in the way the faecal microbiotas of the donors were able to degrade added lipids. Variability in lipid degradation could be correlated with the number and activity of isolated lipolytic bacteria. The mechanism by which orlistat and the GI microbiota cause side-effects in individuals is unknown, but several hypotheses have been proposed to account for their manifestation. The demonstration of great variability in the lipolytic activity of microbiotas to degrade lipids led to a large-scale cultivation-based study of lipolytic/lipase-positive bacteria present in the human faecal microbiota. Of 4,000 colonies isolated from 15 donors using five different agars, 378 strains were identified that had lipase activity. Molecular identification of strains isolated from five donors demonstrated that lipase activity is more prevalent in the human GI microbiota than previously thought, with members of the phyla Firmicutes, Bacteroidetes and Actinobacteria identified. Molecular identification and characterization of the substrate specificities of the strains will be carried out as part of ongoing work.

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