Obesity levels are increasing worldwide, and in the United Kingdom the prevalence of overweight and obesity is amongst the highest in the developed world. Obesity is associated with reduced physical function and health-related quality of life, as well as an increased risk of co-morbidities such as type 2 diabetes and hypertension. As a result of high levels of morbid obesity and a failure of conventional methods of weight loss, more people are resorting to invasive weight loss techniques such as bariatric surgery. Bariatric surgery combined with lifestyle modification is currently the most successful weight loss intervention for the treatment of obesity and its associated co-morbidities. However, weight regain is becoming more apparent, generally occurring between 12 and 24 months after surgery. Weight regain is generally attributed to the failure of individuals to adopt or maintain the necessary lifestyle changes. The most common factors leading to weight regain after bariatric surgery are insufficient exercise and returning to pre-operative eating behaviours. Increasing physical activity after surgery positively affects weight loss and physical function outcomes; therefore, adopting an active lifestyle is fundamental. This thesis combines three research studies which collectively provide evidence for understanding the importance of physical activity for optimising physical function and facilitating the prevention of weight regain. Study one is a systematic review and meta-analysis which assessed pre to post-operative changes in physical activity behaviour and physical function outcomes among obese adults receiving bariatric surgery. This demonstrates improvements in objective and self-reported activity and function by 12 months. Study two is an analysis of body mass, co-morbidity and physical function data from pre to post bariatric surgery. This retrospective NHS dataset analysis aimed to identify if and when weight regain occurs, the proportion of co-morbidity resolution, and physical function patterns in patients after bariatric surgery. Weight loss patterns indicate weight stability from 12 to 24 months and weight regain 24 months post-surgery. Study three is a randomised controlled trial, The MOTION Study, which examined the effect of a 12 week exercise intervention on physical function and body composition in patients 12-24 months post bariatric surgery. This trial also examined maintenance of effects at six months. Findings suggest that implementing exercise at the point of weight regain is effective, notably for improving physical function and body composition in this population. This thesis therefore contributes to advancing the understanding of the role of physical activity in enhancing long-term outcomes after bariatric surgery and to informing future post-operative bariatric care.

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Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 233-251). Available also in a digital version from Dissertation Abstracts.

Thesis (Ph. D.)--University of Texas at Austin, 2000. / Includes vita. Includes bibliographical references: (p. 233-251). Available also in a digital version from Dissertation Abstracts.

Memoria para optar al Título Profesional de Ingeniero de la Madera / Nothofagus obliqua (Mirb.) Oerst (roble o pellín), es una especie que se distribuye desde la Región de Valparaíso hasta la Región de Los Lagos; también habita en Argentina. Esta especie se caracteriza por la alta durabilidad natural que presenta su madera en individuos adultos. Sin embargo, para la madera proveniente de renovales, con diferentes características de color y densidad, no existen antecedentes sobre su comportamiento frente al ataque de hongos de pudrición u otros agentes de biodeterioro. Actualmente, la madera de renovales de roble es sometida a un tratamiento de “vaporizado”, el que tiene como objetivo igualar el color rosado a rojizo del duramen de la madera de renoval, con el rojo oscuro del duramen de roble pellín, mucho más apreciado en el mercado. Con el objetivo de proporcionar antecedentes sobre la durabilidad natural de la madera de renoval de roble y de la influencia del tratamiento de cambio de color (vaporizado), se evaluó la resistencia de estas maderas frente a la acción de hongos de pudrición mediante la pérdida de peso, solubilidad en soda y el % de lignina. Para realizar el estudio se utilizó madera de renoval de roble, empleándose 40 probetas de albura y 40 de duramen. Se aplicó el proceso de vaporizado a 20 probetas de cada grupo, de manera de compararlas con el comportamiento de la madera sin vaporizar frente al ataque del hongo de pudrición blanca Polystictus versicolor y de pudrición café Poria monticola, utilizando además, 20 probetas de roble adulto como testigo. La mitad de las probetas de cada conjunto fue evaluada a los 2 meses (T1) y el resto a los 4 meses (T2) desde el inicio del ataque fúngico. Los resultados indicaron que el vaporizado no tuvo influencia sobre la resistencia de la madera de renoval frente al ataque de P. versicolor, que generó el %PP más alto para todos los tipos de madera a los 2 meses de acción fúngica. Así mismo, el % de solubilidad en soda indicó que el hongo de pudricion blanca provocó el mayor biodeterioro en comparación con el hongo de pudricion café. Para el caso de P. monticola, se observó que el vaporizado tampoco tuvo efecto sobre la resistencia al ataque de pudrición, generándose el mayor biodeterioro a los 4 meses (T2) que a los 2 meses (T1). Esto señaló finalmente, que la madera de renoval de roble no es una madera durable, considerando su resistencia frente al ataque de hongos de pudrición. / Nothofagus obliqua (Mirb.) Oerst (roble o pellín), is a specie allocated from Valparaiso Region to Los Lagos Region, Chile, also it can be found in Argentina. This kind is characterised by its high natural durability of its wood in adults members. Nevertheless, there are not history, for wood from secondary forests, with different characteristics of color and density, about its behaviour against the fungal attack or other biodeterioration agents. Nowadays, the roble wood from secondary forests is subjected to a “steaming” treatment, which aims to equalize pink to reddish heartwood color of the wood from secondary forests, with the dark red of the roble pellin heartwood, much more appreciated in the market. In order to provide history about the natural durability of the roble secondary forest wood, and of the influence of the color change treatment (steaming), the resistance of these woods against the action of fungal through weightloss, soda solubility and the lignin percentage was evaluated. Roble wood (renoval) was used to carry out the research, using 40 test tubes for sapwood and 40 test tubes for heartwood. Steaming process was tested in 20 test tubes of each group to do the comparison with those samples that were not under the process but under the white rot fungi attack Polystictus versicolor and the brown fungi Poria monticola. Also 20 test tubes of old roble were used as reference sample. Half of the samples of each group was checked at two months (T1) and the remaining samples at four months (T2) since the attacks of fungi started. The results shown that the steaming did not affect the wood resistance against the attack of P. versicolor produced the highest %PP for all the samples at 2 months of the test. Moreover, the %S indicated that the white fungi produced a bigger biodeterioration than the brown one. In the case of P. Monticola, it was observed that the steaming had no effect neither about the resistance of fungal attack, generating the greatest deterioration at 4 months (T2) than 2 months (T1). This finally pointed that the roble secondary forest wood is not a durable one, considering its resistance against the fungal attack

This thesis investigates the acceptability and efficacy of Functional Imagery Training (FIT), a motivational intervention for weight-management. FIT is based on Elaborated Intrusion Theory, delivered in the style of Motivational interviewing (MI), and designed to promote sustained behaviour change and address cravings. It trains the habitual use of affective, goal-directed mental imagery of personal incentives, using imagery to plan behaviours, anticipate obstacles, and mentally try out solutions from previous successes. Participants are taught to update their imagery from their experience, and to generalise their imagery skills to new goals. In study 1, focus groups explored problems and wishes in regards to weight-management, including reactions to Functional Imagery Training (FIT) as a possible intervention. The issue of waning motivation and the desire for motivational app support was expressed in all groups. Participants were positive about FIT. Study 2 was an uncontrolled pilot trial of FIT. Eleven out of 17 participants (65%) lost 5% body weight or more by three months. Participants continued to lose weight during an unsupported 12-month period and experienced mean weight loss of 6kg (SD= 5.7; d=1.06) and mean waistline reduction of 11.5 cm (SD= 7.4; d=1.56) at 15 months. Study 3 compared the impact of FIT with MI on motivation and self-efficacy, over the first month of a randomised controlled trial (RCT) for weight-loss. Structured elicitation and training in goal-related imagery, i.e., FIT, increased motivation and self-efficacy for weight-loss relative to MI. Study 4 was the RCT for weight-loss, comparing FIT and MI over an intervention-supported six-month period, followed by six months unsupported. The FIT group achieved clinically meaningful weight-loss at 6 months (M kg-loss=4.11) and continued weight-loss at 12 months (M kg-loss=6.44); the MI group stabilised by 12 months (M kg-loss=.67), after minimal weight loss at 6 months (M kg-loss=.74). Study 5 qualitatively explored experiences of MI and FIT RCT participants, upon completing the 6-month intervention phase. MI participants wished for continued therapist- support and feared relapse. FIT participants described a mind-set-change and were confident they could maintain changes and overcome challenges using imagery techniques. Given the demonstrated benefit of motivational imagery in weight-control, FIT should be considered and further tested as an intervention for health behaviour change.

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.

A considerable percentage of the UK population are overweight (BMI≥25kg/m2) or obese (BMI≥30kg/m2). However, despite living in the same culture and exposed to a similar “obesogenic” environment, some individuals gain weight while others do not (French et al., 1995). This variability in weight control has been suggested to be associated with individual differences in eating behaviours (French et al., 2012). Certain factors, such as motivation (hedonic hunger and hunger status) as well as cognition (impulsivity and memory) may have an impact on eating behaviours and their relationship with weight control. Thus, the objective of this thesis was to explore individual differences in eating behaviours and investigate their relationship with motivation, cognition and weight control. The first experiment (Chapter 2) investigated the relationship between eating behaviours, motivation (hedonic hunger) and food consumption during an ad-libitum buffet. This study suggests that restrained eating behaviour was associated with higher overall energy intake, greater energy intake from unhealthy foods and greater energy intake from both high and low energy dense foods. However, no interactions between restraint and disinhibition or hedonic hunger was seen. Following this, the second experiment (Chapter 3) examined whether eating behaviours, such as disinhibition, restraint and hunger, change during a weight loss and weight maintenance period and whether they could predict changes in weight during these periods. Indeed, the results suggest that lower baseline restraint could predict greater weight loss during a low-energy liquid diet and interventions which increase restraint and decrease disinhibition may be beneficial for longer term weight maintenance. The third experiment (Chapter 4) was designed to investigate whether motivation and cognition influences eating behaviours. The results suggest that hedonic hunger, restraint and impulsivity may lead to higher levels of disinhibited eating behaviour. This study was also able to replicate the findings of previous literature suggesting that episodic memory is negatively associated with BMI (Cheke et al., 2016). Finally, following on from the previous study results, the fourth experiment (Chapter 5) included a more diverse sample of participants including dieters. The results provide evidence that individuals on a diet have poorer episodic memory ability than those currently not on a diet. This study also extended previous results suggesting that hedonic hunger (but also episodic memory and hunger) are important factors in disinhibited eating. Hedonic hunger was also shown to be important in levels of hunger.

Weight loss maintenance is essential for the reduction of obesity-related health impairments. However, only a minority of individuals successfully maintain reduced weight in the long term. Research has provided initial evidence for associations between weight-related teasing (WRT) and greater non-normative eating behaviors. Further, first evidence was found for associations between non-normative eating behaviors and weight loss maintenance. Hence, the present study aimed to examine the predictive value of WRT for weight loss maintenance and the role of non-normative eating behaviors as possible mediators of this relationship. The study was part of the German Weight Control Registry that prospectively followed individuals who had intentionally lost at least 10% of their maximum weight and had maintained this reduced weight for at least one year. In N = 381 participants, retrospective WRT during childhood and adolescence, current non-normative eating behaviors (i.e., restrained, external, emotional eating), and change in body mass index (BMI, kg/m2) over two years were examined using self-report assessments. Structural equation modeling was used to analyze the assumed mediational relationship. As a result, a greater effect of retrospective WRT during childhood and adolescence predicted less successful adult weight loss maintenance over two years. Current emotional eating fully mediated this relationship while current restrained and external eating yielded no mediational effects. Hence, a greater effect of WRT predicted greater current emotional eating, which in turn predicted a smaller decrease or a greater increase in BMI. Our findings suggest that suffering from WRT during childhood and adolescence might lead to emotional eating which in turn impairs long-term weight loss maintenance. Thus, our results highlight the need for interventions aiming at reducing weight stigmatization and targeting emotional eating for successful long-term weight loss maintenance.