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The game of soccer places various physiological demands on players, who are required to respond by carrying out a range of locomotor activities at different intensities. Such activity patterns contribute to a high energy turnover in both training and match-play, which in turn requires the intake of adequate fuel sources to sustain it. Adequate nutrient intake constitutes an important foundation for physical performance by providing fuel for biological work, both short and long term as required throughout the course of a soccer match. Despite the popularity of the sport worldwide, few studies investigating the effect of nutrition on performance in soccer have been conducted to substantiate the effect of optimal nutrition over the duration of a standard soccer match. This dearth of evidence has contributed in turn to a lack of specific nutrition guidelines for soccer players, coaches, sport scientists, nutritionists and club administrators. The aim of this thesis is to investigate the physiological, psychological and sociological aspects of nutrition and soccer, and posit a comprehensive nutritional framework to actively engage soccer players in adopting diets supportive of optimal performance in soccer training and match-play. The researcher set out by hypothesising that an optimal diet positively influences physical performance in soccer match-play. To test this hypothesis, a 90 h diet was developed for the participating semi-professional soccer players. Following implementation of the diet, a 90-minute soccer-specific simulation protocol, BEAST90mod was used to test its effects on physical performance in soccer. The remaining three inter-linked studies were longitudinal in nature, and carried out with participants forming part of the Malta U21 National Soccer Team. In the first instance, players’ habitual dietary intake, expenditure and energy balance was examined. The researcher then gathered information about the players’ knowledge, attitudes, habits, perceptions and barriers towards a diet conducive with optimal soccer performance. The same players finally underwent a 9-month nutritional education and support intervention, the efficacy of which was measured by the researcher throughout the intervention period. The principle aim of the research is to present findings that provide players and stakeholders in soccer a clear indication of the effects of specialist nutrition in soccer, and empower them with a range of appropriate tools and strategies as employed throughout the support programme. It ultimately seeks to improve physical performance in soccer training and match-play by informing sound individual and team approaches to nutritional decision-making.

This thesis compared the effect on weight loss of either replacing diet beverages (DBs) with water or continuing to consume DBs (study 1 in healthy overweight and obese, n=89 and study 2 in patients with type 2 diabetes, n=81) adults during a 24-wk weight-loss program (for study1 and 2) and 18 month weight loss and weight maintenance plan (for study3, n=89). In study 1, compared with the DB group, the water group had a greater decrease in weight (1.2kg more weight loss in the water group compared with the DBs Group ,P=0.015), BMI (0.5 kg/m² more BMI reduction in the water compared with the DBs Group ,P=0.002), fasting insulin (1 mU/l more Fasting insulin reduction in the water compared with the DBs Group,P < 0.001), homeostasis model assessment of insulin resistance (HOMA-IR)(0.2 more HOMA-IR reduction in the water compared with the DBs Group, P < 0.001) and 2-h postprandial glucose(0.305 mmol/l more 2hpp reduction in the water compared with the DBs Group,P < 0.001). In study 2, weight (2.5 kg more weight loss in the water compared with the DBs Group, P=0.005) and BMI (0.9 kg/m² more BMI reduction in the water group compared with the DBs Group, P=0.005) decrease after 18 months in the water group compared with the DBs group was significant. There was also a greater reduction in fasting insulin levels (1.8 mU/l more Fasting insulin reduction in the water group compared with the DBs Group,P < 0.001), better improvement in HOMA-IR (0.5 more HOMA-IR reduction in the water group compared with the DBs Group, P < 0.001), a greater decrease in 2-h postprandial plasma glucose (0.5 mmol/l more 2hpp reduction in the water group compared with the DBs Group, P < 0.001) and glycated hemoglobin (0.2 more HbA1c reduction in the water group compared with the DBs Group, P=0.030) in the water group compared with the DBs over 18 months. In study 3, obese participants with Type 2 diabetes in the water group of study 2 had more weight loss (1.16 kg more weight loss in the water group compared with the DBs Group, P=0.006) and BMI (0.5 kg/m² more BMI reduction in the water group compared with the DBs Group, P=0.006). Also reduction of fasting insulin (1.6 mU/l more Fasting insulin reduction in water group compared with DBs Group,P < 0.001), fasting plasma glucose (0.3mmol/l more Fasting plasma glucose reduction in the water group compared with the DBs Group, P=0.003), HOMA-IR (0.7 more HOMA-IR reduction in the water group compared with the DBs Group, P=0.003) and 2 hour postprandial glucose (0.3 mmol/l more 2hpp reduction in the water group compared with the DBs Group, P=0.027) was greater in the water group. By contrast, changes in waist circumference and lipid profiles were not significantly different between the two groups in these three studies. Replacement of DBs with water after the main meal in obese and overweight healthy and type 2 diabetic women who were regular users of DBs may cause greater weight reduction during 24 weeks and also in the longer period of an 18 month weight management program. In addition, replacement of DBs with water offers clinical benefits to improve insulin resistance. Generally, better improvements in energy and carbohydrate metabolism may occur when water rather than DBs is consumed over a weight loss program.

Background Obesity is a highly complex, chronic disorder with a multifactorial aetiology that includes biological, psychosocial and cultural factors. Since the discovery of oil in 1959, Libya has been undergoing a nutrition transition. Despite obesity reaching epidemic proportions in Libya, there is a lack of information about obesity in Libyan adults. Aims The aims of this study were to investigate the risks and protective factors associated with obesity among adult men and women in Libya; to estimate gender differences in the prevalence of obesity among Libyan adults; and to explore key informants’ views about obesity within the context of Libyan culture. Design of study An adapted mixed-methods sequential explanatory design was used, consisting of two phases: a quantitative study in the form of a cross-sectional design, and a qualitative study in the form of semi-structured interviews, which followed up on the findings of the first phase. Method A multi-stage cluster sampling technique was used to select participants from the Benghazi electoral register. With a response rate of 78%, the sample consisted of 401 Libyan adults, aged 20-65 years, who have lived in Benghazi for over ten years; 63% were female. A survey questionnaire was used to examine the relationship between Body Mass Index (BMI) and the following four-predictor variables, derived from the Socio-Ecological Model (SEM): socioeconomic status; unhealthy eating habits; physical activities and sedentary lifestyle; and neighbourhood environment. Anthropometric measurements were collected from participants in their homes. For the qualitative phase, 9 Libyan healthcare professionals and 12 Libyan community leaders (key informants) were individually interviewed. A mixed-methods approach to study obesity has not previously been used in Libya. Results The prevalence of obesity among Libyan adults was found to be 42.4%, whereas that of being overweight was 32.9%. A significant positive association was found between obesity and two SES components (education level and income) in Libyan adults of both genders, while occupational status was significantly positively associated with obesity in women only. Obesity was significantly positively associated with fast-food consumption, and the consumption of large food portion sizes, in Libyan adults of both genders. In contrast, the consumption of sugar-sweetened beverages was significantly positively associated with obesity in Libyan women but not in men. A significant inverse association was found between breakfast consumption and obesity in Libyan adults. Obesity was significantly negatively associated with physical activity in Libyan women, while significantly positively associated with sedentary behaviour in Libyan women but not in Libyan men. Finally, a significant association exists between the BMI of Libyan adults in 6 of the 12 neighbourhood environment attributes. For Libyan men and women these were: street connectivity, ‘unsafe environment and committing crimes at night’, and neighbourhood aesthetics. For men only, these were: access to public transport, access to recreational facilities, and ‘unsafe environment and committing crimes during the day’. Finally, ‘residential density zones’ was significant for women but not for men. Three main risk factors were identified from the qualitative study. The first concerned the heavy subsidisation of staple food commodities in Libya; the second is Libya’s deteriorating health sector performance; and the third is the effect of the neighbourhood environment on physical activity and food, including the current political and economic instability in Benghazi which is potentially fuelling the obesity epidemic. These themes and additional sub-themes were categorised as belonging to one of the five spheres of the SEM (individual; interpersonal; institutional and organisational; community and physical environment; and public policy), resulting in the final conceptual framework of this study. Some of the qualitative results contradicted the quantitative results, resulting in some inconclusive findings. Conclusion These findings could inform Libyan health policies and the interventions that are urgently needed for preventing or controlling the obesity epidemic in Libya. Key recommendations are that an electronic health information system needs to be implemented and awareness about obesity and its causes and consequences needs to be raised among the public in order to dispel the many myths and misconceptions held by Libyans about obesity.

A controlling maternal feeding style can have negative consequences for child weight and eating style (Ventura & Birch, 2008). Mothers who breastfeed during the first year exert lower levels of control over child feeding (Farrow & Blissett, 2008). Explanations for this relationship speculate that experience of breastfeeding reduces control as breastfeeding requires an infant-led approach (Taveras et al. 2004) or alternatively that maternal attitudes predict both initiation of breastfeeding and later maternal control (Farrow & Blissett, 2006a). The nature of this relationship is explored in this thesis. Mothers reported their intended and actual feeding style during milk feeds when pregnant and at six months postpartum using a modified version of the Child Feeding Questionnaire (Birch, Fisher, Grimm-Thomas, Markey, Sawyer, & Johnson. 2001). Maternal use of control in the form of scheduling and encouraging milk feeds was evident. A high level of control was associated with a shorter breastfeeding duration (p < 0.001). Control beliefs were present prenatally with intended breastfeeding duration inversely associated with intended control. Furthermore, attitudes towards the infant-led nature of breastfeeding were associated with both breastfeeding duration and control. Breastfed infants need to be fed to infant demand and amount consumed is immeasurable whilst formula feeding is open to maternal manipulation. A belief that breastfeeding was inconvenient was associated with scheduling feeds whilst concerns over milk intake and low confidence were associated with encouraging feeds. Whilst scheduling feeds was a stable behaviour predictive from prenatal intention, encouraging feeds was fluid and related to maternal experience. Concerns about infant size or feeding difficulties increased use of encouraging feeds. Maternal desire for control may therefore drive breastfeeding duration, explaining the association between breastfeeding and later feeding style. The findings have important implications for breastfeeding duration, early programming of appetite and bodyweight and later maternal feeding style.

The emergence of obesity as a distinct disease could have far reaching consequences for an organisation where optimum health and physical fitness are required for personnel to perform their occupational roles effectively. The aim of this thesis is to increase our understanding of the prevalence, correlates and predictors of obesity in the British Army. Systematic review indicated a smaller body of knowledge in respect of the treatment and correlates of obesity in military populations. Successful treatment interventions incorporated exercise, healthy eating information, behavioural modification, self-monitoring, relapse prevention, structured follow-up and were supported by trained personnel. The major significant correlates of obesity were being enlisted personnel, male, ≥35 years of age, African-American/Hispanic ethnicity, and married (with spouse present). The review highlighted the deficit in knowledge concerning treatment, and correlates of obesity in military populations. The trend of escalating obesity has prompted some armed forces to report obesity trends and prevalence, the findings of which suggest that obesity is a growing concern in the armed services. A study based on the secondary analysis of data covering 50,000 British Army soldiers indicated that according to BMI, 56.7% of the study population were overweight and of those individuals 12% were obese. When waist circumference data were added to the BMI data, the results indicate that females displayed a higher percentage of risk of obesity related ill-health (a combination of BMI and waist circumference) than males (30.4% and 24% respectively). Further analysis suggested that age, marital status, rank and military employment category were significant correlates of obesity. Additionally, obesity and increased risk of obesity related-ill-health were linked to higher failure and lower attendance on British Army physical tests. Data suggested older army personnel (>30) had a higher pass rate, but a lower attendance rate. The final analysis of all available variables suggested physical test outcome, age, medical status and enlisted status were the most significant predictors of obesity. A final study based on a different study population (n=1124) from the high readiness component of the UK based British Army sought to identify relationships between health behaviours that were not supportive of healthy weight and to understand the predictive influence of individual and collective behaviour in relation to obesity and the risk of obesity related ill-health in military personnel. The investigation used a health behaviour questionnaire to assess health behaviours that might influence weight status. Final analysis of this highly active population suggested, restrained eating, food preparation in the working week, injury status, age, sedentary behaviour, leisure-time physical activity engagement and type of motivation for exercise were the most significant factors. This thesis highlights the lack of knowledge, and gives evidence to support the impact of obesity on individual health and collective occupational capability. Obesity is a complex multifaceted disease where no single causal route predominates. However, the identification of potential causal and predictive relationships will aid in the prevention and treatment of obesity in the British Army.

Lifestyle choices threaten to compromise health and performance of trained athletes. This thesis presents a series of studies which broadly investigated the impact of nutritional and physical challenges to human health and performance. The potential causes and effects of fluid imbalances on physical health, immune function and athletic performance were investigated. Certain populations experience chronic low-level hypohydration and athletes often fail to rehydrate sufficiently between exercise sessions. The long-term implications of hypohydration are not fully understood, but are suggested to be associated with chronic disease. In this thesis, maintenance of fluid balance was observed in healthy males, despite a caffeine intervention thought to cause diuresis. Furthermore, when mild hypohydration was induced by 24-h fluid restriction, there was little impact on mucosal immunity during endurance exercise compared with euhydration. The impact of intensified training (IT) on the physical, mental, hormonal and immunological status of well-trained athletes was investigated. A performance-specific nutritional intervention was implemented to investigate the effects of nutrient availability during prolonged exercise training sessions. Phases of IT are a regular feature of a periodised training programme. However, an imbalance between training and recovery can have significant implications for long-term athletic performance and general wellbeing. Changes in neuroendocrine, neurobiological and mucosal immune function were observed during IT and some potential markers of overreaching and were identified. Further research is required before practical application of these markers can be used effectively in the field. A relatively short period of IT resulted in significant disruptions to mood state and sleep quality. Minor changes in exercise performance were observed. Markers of overreaching were highly individual, as were responses to training.

Currently there is limited research addressing the eating behaviours of preadolescent children, despite evidence suggesting that friends and peers may contribute to the developing eating attitudes and behaviours of children of this age. Eating behaviours in terms of this thesis include both under- and over- eating behaviours, with a specific focus on the under-eating behaviour, dietary restraint, and the over-eating behaviours emotional eating and external eating. The fundamental aim of this thesis was to examine friend and peer influences on children s eating behaviours, with a specific focus on a community sample of preadolescent children. Based on links established in the literature between childhood eating behaviours (dietary restraint, emotional eating and external eating) and parental controlling feeding practices (pressure to eat and restriction) and childhood symptoms of anxiety and depression, these factors were also considered alongside the contribution of friends and peers, both cross-sectionally and longitudinally. The longitudinal stability and continuity of self-reported eating behaviours and perceived parental feeding practices in preadolescent children were also examined in this thesis. A pilot study and experimental study provided an objective measure of children s snack food intake following a school lunchtime, when offered a selection (healthy and unhealthy) of snack foods in the presence of friends and peers. Links between food intake in the presence of friends and peers, and self-reported eating behaviours, parental controlling feeding practices, child symptoms of anxiety and depression and BMI were further explored. The research in this thesis suggests that friends dieting behaviours predict individual children s dieting behaviours, and also highlights links between problematic eating and anxiety in preadolescent children. Parental controlling feeding practices were found to have a negative impact on preadolescents eating behaviours and were also found to be potentially linked to the development or maintenance of anxiety and depression symptoms in children of this age. Preadolescents reports of eating behaviours and perceptions of the controlling feeding practices their parents utilised with them were stable over time, but, with the exception of restriction, lacked continuity. Dietary restraint, emotional eating and external eating decreased over a 12 month period. While some of the research in this thesis requires replication, the results present many novel and interesting findings. Using longitudinal and experimental data, the research reported on in this thesis highlights the important contributions of friends, peers, parents and individual anxiety and low mood to the eating attitudes and behaviours of preadolescent aged children.