Rozprawy doktorskie na temat „Weight loss”

The purpose of this study was to examine individuals’ perceptions of weight loss and weight loss methods. Respondents were employees and customers attending health/wellness events at local supermarkets in June, July, and August 2019. Participants completed a survey to assess their understanding and perceptions of weight loss and methods used to achieve weight loss. The majority of participants were white females, 60 years or older with a college degree and a Body Mass Index (BMI) classified as overweight or obese. Data revealed most participants had a variety of misconceptions relating to weight loss and weight loss methods that were obscure and fad-diet oriented, including low-carbohydrate diets. Participants did understand benefits of weight loss but expressed maintaining weight loss was a challenge. These findings suggest that fad diets are alluring to individuals and individuals did not incorporate evidence-based behavior changes to promote or sustain weight loss.

Psychosocial differences between weight loss maintainers and weight loss non-maintainers were compared at least one year after reaching a medically approved weight goal through a medically supervised weight loss program. Research questions addressed differences between groups on the dimensions of somatization, obsessive/compulsive issues, interpersonal sensitivity, depression, anxiety, hostility, ability to resolve past emotional issues, social interpersonal relationships, and tolerance of ambiguity. The all-female sample consisted of maintainers of weight loss (N=30), non-maintainers (N=33), psychotherapy maintainers (N=14), and psychotherapy non-maintainers (N=ll). Research instruments administered were the Symptom Checklist-90-Revised, Fundamental Interpersonal Relations Orientation-Behavior, Personal Orientation Inventory, and Budner Scale for Tolerance/Intolerance of Ambiguity. To determine differences between groups, a t test was performed on data relating to the maintaining and non-maintaining groups. An analysis of variance was performed on data related to the maintaining, non-maintaining, psychotherapy maintaining, and psychotherapy non-maintaining groups. An intercorrelation matrix was completed for all variables. Non-maintainers of weight loss had significantly more difficulty with somatic problems as indicated in the results of both the t test and the analysis of variance (p < .009, p < .02, respectively). Non-maintainers expressed more complaints which focused on cardio-vascular, gastrointestinal, respiratory, and somatic equivalents of anxiety (headaches, pain, discomfort of the gross musculature). An analysis of variance showed non-maintainers (p < .05) to be significantly less effective in resolving past emotional issues than maintainers, psychotherapy maintainers, and psychotherapy non-maintainers. Non-maintainers were more burdened by guilt, regrets, and resentments from the past. Results of the analysis of variance indicated that psychotherapy maintainers (p < .03) were more socially adjusted than maintainers, non-maintainers, and psychotherapy non-maintainers. Inclusion and control subscales characterized psychotherapy maintainers to be more socially adaptable and flexible. They assumed responsibility without support of others and were less burdened with fears of helplessness and incompetence.

Two thirds of Americans are overweight or obese. Traditional obesity interventions (e.g. drug therapy, diets, behavior therapy) generate moderate short-term weight loss but have little evidence of long-term weight maintenance. The cultural phenomenon of "yo-yo dieting" mirrors empirical findings which suggest that weight loss, albeit demanding, is a far easier process to target than weight maintenance. The present study sought to evaluate the efficacy of an acceptance based behavioral intervention designed to generate improvements in psychological health and quality of life in obese and overweight adults as well as encourage gradual and sustainable weight loss. The therapy package combined the traditional behavioral interventions of self-monitoring and goal setting with an Acceptance and Commitment Therapy (ACT) protocol across eight weekly individual therapy sessions. While no significant immediate weight loss was observed following the intervention, significant improvements in general psychological health, reductions in anxiety and escape maintained eating, and increases in weight related acceptance and action were found in the treatment group (n = 9) compared to a wait list control group (n = 10). These findings suggest that an acceptance based intervention targeting wide band outcomes might serve as a viable alternative to traditional approaches targeting only immediate weight loss.

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The only way to lose fat weight is to consume fewer calories than the body uses. Athletes who successfully lose weight learn how to apply this concept, while maintaining the energy levels required for training.

The aim of this thesis was to investigate obesity and weight change in two English prisons using both qualitative and quantitative methods. The research incorporated the first study to assess UK male prisoners’ weight change during imprisonment, as well as the first study to take into consideration factors associated with weight change specific to the prison setting. Data collection, for both qualitative and quantitative components of the study, started in May 2013 and ceased in November 2015. Qualitative interviews were undertaken with prison nurses (17 interviewees) and prisoners (19 interviewees) to obtain an understanding of how imprisonment and the prison setting can influence a prisoner’s weight. These interviews showed similar findings with both groups identifying food and physical activity as important factors that might influence a prisoner’s weight. These opinions were similar to views that might be expressed in a community setting. However, in addition, both groups identified how imprisonment and the prison environment created a unique setting for weight management. These contextual factors influenced health related behaviours and provided a greater understanding of the determinants of prisoners’ health. Power was a key theme, shown to exist in many different forms and having a positive and negative influence on prisoners’ health related behaviours. These were shown to be influenced by three main sources of power: the prison, other prisoners and impact of the outside world. Time, in various forms, was also found to play an important role in dictating prisoners’ health-related behaviours. The quantitative study demonstrated the complex relationship between imprisonment and weight and the influence of age on weight change. Findings from the quantitative study supported the results from the two qualitative studies showing how prison culture impacted on weight and weight change. The final discussion utilises various models of embodiment, including those specific to men’s health, to understand the results of this research project. The final conclusion challenges some commonly held perceptions of prisoners’ health related behaviour and provides a theoretical model that could be developed to provide more appropriate care for prisoners in the future.

This thesis presents four studies which explore factors associated with weight status, weight loss and attrition. The first and second studies, respectively, examine factors associated with weight loss and attrition. The third study utilises statistical methods to detect and correct for sample selection bias on expected weight loss outcomes and the final study examines risk and time preferences in relation to BMI. Overall we identify several variables exhibiting a significant relationship with weight loss and attrition. Further, we identify and correct for non-random sample selection and, in the final research chapter, find some evidence of a relationship between risk preferences and BMI. Whilst the four research chapters presented can be read independently, each chapter builds upon the findings of the previous studies to present a rich and comprehensive assessment of variables of interest, and throughout the thesis we build an increasingly sophisticated methodological approach to the evaluation of weight status, weight loss and attrition. Our research allows for the identification of potential intervention-generated-inequalities, which are of particular importance for both the continuous development of weight management services and policy. For the first time within the current literature we complement a rich, comprehensive assessment of weight management services with sophisticated quantitative methodological approaches and concepts prevalent in the behavioural economics literature but which have rarely been utilised in studies of obesity. Finally, we evidence a requirement to control for sample selection in economic assessments of weight management services to ensure unbiased estimates within cost-benefit and return-on-investment analyses.

Hypothesis: The work examined the effect of rate and extent of WL on body composition, physiological function (e.g. respiratory function), psychological function (e.g. mood), appetite and behaviour. Methods: The PhD was designed as a series of structured, longitudinal studies examining specific physiological and psychological parameters, in the three groups of six healthy, but obese (BMI 30-35) men. Subjects were assigned to either a WL group: (1) total fast to achieve 5% WL in 6 days; (2) VLCD (2.5 MJ/d) to achieve 10% WL in 3 weeks; (3) LCD (5.0 MJ/d) to achieve 10% WL in 6 weeks. Results: The main findings of this thesis are, (i) There was little evidence of energy balance regulation in response to an acute total fast (36 h) in human subjects; (ii) Rate of WL is important in determining tissue loss. A slowest rate of WL (with LCD) induced the greatest loss of fat mass, relative to lean tissue. The VLCD only had a protein sparing effect, relative to fasting, after initial loss of LBM; (iii) Rate of WL had a pronounced effect on subjectively-rated fatigue. This, in turn, influenced physical activity and hence total daily energy expenditure. The faster the rate of weight loss, the more fatigued the subject felt. WL had no effect on muscle function nor central nervous fatigue; (iv) Fasting is a stressful means of weight loss leading to a negative mood, which was reversed upon re-feeding. Extent of WL positively influenced mood; (v) All groups cognitively restrained ad libitum intake, post weight loss. There was a negative correlation between increased restraint score and body weight maintenance (-0.519; p=0.027). Conclusion: Rate and extent of WL are both important in determining the success of WL in terms of tissue loss, health, well-being and quality of life. Starvation cannot be recommended as a means of WL. The most effective WL strategy, should be a LCD, conducted over a period of weeks, resulting in a slow rate of WL to maximise fat loss and health benefits.

It is not yet clear whether women who lactate lose the weight gained during pregnancy faster than their nonlactating counterparts. The primary objective of this study was to look for any important differences in the rate of postpartum weight loss in the first 9 months postpartum according to method of infant feeding.
Two hundred thirty-six women attending two public health clinics in Montreal were weighed in one to four encounters occurring at different stages of the postpartum period but no later than the 9th month postpartum. A questionnaire assessing the method of infant feeding (predominantly breastfeeding, mixed feeding or predominantly bottlefeeding) and potential confounders was administered by telephone after each weighing. An unbalanced multivariate repeated measures analysis revealed no statistically significant differences in the rate of weight loss by category of infant feeding. Gestational weight gain, postpartum smoking and maternal birthplace were important predictors of postpartum weight change.

In the United States and many other countries, obesity is viewed as a public health crisis that must be handled. Many social and individual solutions to the problem are proposed in research and policy. On an individual level, many Americans try to get rid of their fat with a multitude of weight loss practices as part of a healthy lifestyle. Obesity rates, feelings towards fatness, and weight control behaviors are significantly affected by a number of sociocultural factors. In this project I explore the relationship between the desire to lose weight and weight control practices with income. Using data from the National Health and Nutritional Examination Survey (NHANES) 2009-2010 (N=4,341), I explore how income is associated with body satisfaction and weight control behaviors. I then examine if specific weight loss strategies differ by SES among those who have tried to lose weight (N=1,512). Results indicate that income impacts the desire to lose weight, weight loss attempts (OR=.778, CI=.663-.913), and some weight control strategies such as exercise (OR=1.392, CI=1.055-1.836), switching to lower calorie foods (OR=1.364, CI=1.027-1.813), and eating less fat to lose weight (OR=1.449, CI=1.094-1.919). However, other sociodemographic characteristics, such as education, gender, and race, played very important roles in predicting these behaviors. Overall, these findings suggest that an individual’s socioeconomic status influences feelings about one’s weight and what one does to change it, but it is only one piece of the puzzle. This study has several implications; most notably that one-size-fits-all obesity solution policy platform cannot be created if real changes are expected. Tailoring interventions to specific groups based on education and income are important to creating lasting change.

Acute dehydration is a common method of weight loss in many combat sports, including Mixed Martial Arts (MMA). Acute dehydration has been shown to negatively affect exercise performance but minimal research has examined the mechanisms influencing exercise performance and potential strategies to mitigate them. The present thesis aimed to: i) examine the prevalence of weight loss methods and magnitude of weight lost in MMA and other combat sports, ii) examine the physiological and psychobiological mechanisms (neuromuscular function, mood and cognitive performance) that may be responsible for acute dehydration-induced decreases in performance, and iii) determine if heat acclimation with and without fluid restriction can minimise the effects of acute dehydration. In Study One, 637 combat sports athletes completed a questionnaire to determine their weight loss practices used prior to competition. MMA athletes reported the highest usage of sauna (76%) and water loading (67%) whilst also reporting the second highest use of training in rubber/plastic suits (63%). In Study Two, fourteen MMA athletes completed a familiarisation session, followed by two experimental sessions during which physiological and psychobiological responses were assessed following acute dehydration or a control trial. During the dehydration session athletes lost 3% of their body mass while in a heated chamber (40˚C and 60% relative humidity (RH)) wearing a sweat suit for 3 h. Participants were then provided with a 3 h recovery period to consume food/fluids, after which neuromuscular fatigue, mood and cognitive performance were assessed. Strength-endurance was impaired following acute dehydration despite no influence on markers of central and peripheral fatigue. However, athlete fatigue perception increased which could indicate impaired performance resulted from mental fatigue. In Study Three, a total of 20 recreationally trained athletes were randomly assigned into two groups and completed 3 weeks (12 sessions) of heat acclimation (passive exposure at 40˚C and 60% RH), either with (HAW) or without (HANW) fluid replacement. On two occasions prior to (i.e. double- baseline) and one following heat acclimation, participants also performed experimental trials. These trials involved 3 h of passive heating (45°C, 38% relative humidity) to induce dehydration followed by 3 h of ad libitum food and fluid intake after which participants performed a repeat sled-push test to assess physical performance. No meaningful differences in performance, physiology or psychobiology were observed between the HAW and HANW groups at any time point. Pooled data revealed that mean sprint speed was faster following heat acclimation compared with baseline data. Heat acclimation appeared to improve mood following dehydration, which could have improved repeat-effort performance via altered fatigue perception. This research provides a better understanding of the prevalence of acute weight loss in combat sports and the mechanisms by which such weight loss impairs exercise performance. The results support heat acclimation as a possible strategy to reduce the negative performance effects of rapid weight loss achieved through acute dehydration.

Men and women have similar rates of obesity but the combined prevalence of overweight and obesity is higher among men. Men who are overweight are a high-risk group for many obesity-related chronic diseases, as they are more likely to carry excess weight in the abdomen, which is generally more harmful than weight stored in the lower body. Men are also less likely than women to perceive themselves as overweight, and thus are less likely to initiate weight loss through organized weight loss programs. On average, less than 27% of weight loss trial participants have been men. Internet-based research is a low-cost, efficient way to produce novel hypotheses related to weight loss that may have previously escaped weight loss professionals. Additionally, incentives are an effective tool to motivate behavior change, and there is ample evidence to support the use of incentives to encourage many health-promoting behaviors, such as weight loss. The purpose our initial study was to facilitate intervention development by using crowdsourcing to detect unexpected beliefs and unpredicted barriers to male weight loss. The aim of our main study was to evaluate the impact of financial incentives to facilitate weight loss in men, delivered as part of a weight loss intervention. Two separate studies were conducted. In the first project, participants were recruited to a crowdsourcing survey website which was used to generate hypotheses for behaviors related to overweight and obesity in men. Participants provided 21,846 responses to 193 questions. While several common themes seen in prior research were revealed such as previous health diagnoses and physical activity participation, other potential weight determinants such as dietary habits, sexual behaviors and self-perception were reported. Crowdsourcing in this context provides a mechanism to further investigate perceptions of weight and weight loss interventions in the male population that have not previously been documented. These insights will help guide future intervention design. For the main project, a randomized trial compared the Gutbusters weight loss program (based on the REFIT program) alone with Gutbusters with escalating incentives for successful weight loss. The six-month intervention was conducted online with weekly in-person weight collections for the first 12 weeks. Gutbusters encouraged participants to make six 100-calorie changes to their daily diet, utilizing a variety of online lessons targeting specific eating behaviors. Measures included demographic information, height, weight, waist circumference, and body fat percentage. Participants (N=102, 47. 0± 12. 3 yrs old, 32. 5 kg/m2, 80. 4% with at least two years of college) were randomized in a 1:1 ratio to Gutbusters or Gutbusters+Incentive. Significantly more Gutbusters+Incentive participants lost at least 5% of their baseline weight compared to the Gutbusters group at both 12 and 24 weeks. Similar to the aforementioned REFIT program, Gutbusters participants were able to achieve clinically significant weight loss. The Gutbusters+Incentive achieved greater rates of weight loss than the Gutbusters alone group, further supporting the value of incentives in promoting health behaviors.

Background: The prevalence of obesity is higher in adults with intellectual disabilities (ID) than in the general population, with increased rates of secondary health risks and increased mortality rates. Multi-component weight loss interventions have been advocated by current UK clinical guidelines for all adults without ID. Such interventions incorporate dietary changes that produce an energy deficit, increased levels of physical activity and the use of behavioural approaches to promote and sustain changes in physical activity and dietary patterns, followed by a weight maintenance intervention. However, UK clinical guidelines have reported that the evidence base for the treatment of obesity in adults with ID is minimal. New evidence in this area of research could be used for the development of accessible weight management interventions for adults with ID and lead to a sustainable clinically significant weight loss. Methods: Study 1: A systematic review aiming to evaluate the clinical effectiveness of weight management interventions in adults with ID and obesity using recommendations from current clinical guidelines for the management of obesity in adults. Full text papers published between 1982 to 2011 were sought by searching the Medline, Embase, PsycINFO and CINAHL databases. Studies were evaluated based on 1) intervention components, 2) methodology, 3) attrition rate 4) reported weight loss and 5) duration of follow up. The assessment of the quality of the studies and interventions was based on the criteria of the Centre for Reviews and Dissemination (CRD) (University of York) and the PRISMA checklist. Study 2: The evidence base for the development of weight maintenance interventions in adults with ID is limited. This study presents the findings of the second phase of a multi-component weight management programme for adults with ID and obesity (TAKE 5). A total of 31 completers of the 16 week weight loss intervention of the TAKE 5 programme were invited to participate in a 12 month weight maintenance intervention. The TAKE 5 weight maintenance intervention included monthly one to one sessions and monthly phone calls, using the recommendations of the Glasgow and Clyde Weight Management Service (GCWMS) and of the National Weight Control Registry. The intervention provided a dietary advice based on the estimated energy requirements of each participant, advice to improve physical activity and behavioural approach techniques to facilitate changes in physical and dietary patterns. Participants’ body weight, BMI, waist circumference (WC) and levels of physical activity were measured before and after the intervention. Paired t tests were used to assess differences in anthropometric and physical activity measurements. Study 3: 52 participants of the TAKE 5 weight loss programme were individually matched by baseline characteristics (gender, age and BMI) with two participants without ID of the GCWMS programme. Non parametric significance tests were used for comparisons between groups in terms of weight and BMI change and rate of weight loss. In addition, data from the 52 completers with ID of the TAKE 5 weight loss intervention were used to perform a univariate logistic regression analysis for the identification of socio-biological predictors for absolute weight loss and clinically significant weight loss at 16 weeks. Study 4: Semi-structured interviews were used to explore the experiences of 24 carers that supported participants of the TAKE 5 weight loss programme. The transcripts were analysed qualitatively using the qualitative data software analysis package, ATLAS ti 5.2 software. Thematic analysis was used to examine potential themes within data. Results: Study 1: Twenty two studies met the inclusion criteria. The interventions were classified according to inclusion of the following components: behaviour change alone, behaviour change plus physical activity, dietary advice or physical activity alone, dietary plus physical activity advice and multi-component (all three components). The majority of the studies had the same methodological limitations: no sample size justification, small heterogeneous samples, no information on randomisation methodologies. Eight studies were classified as multi-component interventions, of which one study used a 600 kilocalorie (2510 kilojoule) daily energy deficit diet. Study durations were mostly below the duration recommended in clinical guidelines and varied widely. No study included an exercise program promoting 225-300 minutes or more of moderate intensity physical activity per week but the majority of the studies used the same behaviour change techniques. Three studies reported clinically significant weight loss (≥ 5%) at six months post intervention. Study 2: 28 participants completed the TAKE 5 weight maintenance intervention. Most of the participants (50.4%) maintained their weight (mean weight change=-0.5kg; SD= 2.2) within ± 3% from initial body weight at the end of the weight maintenance intervention. There was no statistically significant change in BMI and WC at 12 months from BMI and WC at the end of the 16 week weight loss intervention. There was no statistically significant decrease in the time spent in sedentary behaviour and no statistically significant increase in the time spent in light and in moderate to vigorous physical activity. At the end of the weight maintenance intervention participants spent less days walking (at least 10 minutes) than at the end of the end of the weight loss intervention (P<0.05). Study 3: There were no significant differences between participants with ID and participants without ID in the amount of weight loss (median:-3.6 vs. -3.8, respectively, P=0.4), change in BMI (median: -1.5 vs. -1.4, P=0.9), success of achieving 5% weight loss (41.3% vs. 36.8%, P=0.9) and rate of weight loss across the 16 week intervention. Only, initial weight loss at four weeks was positively correlated with absolute weight loss at 16 weeks (P<0.05). Study 4: Three themes emerged from the analysis: Carers’ perceptions of participants’ health; barriers and facilitators to weight loss; and carers’ perceptions of the weight loss intervention. Data analysis showed similarities between the experiences reported by the carers who supported participants who lost weight and participants who did not. Lack of sufficient support from people from the internal and external environment of individuals with ID and poor communication among carers, were identified as being barriers to change. The need for accessible resources tailored to aid weight loss among adults with ID was also highlighted. Conclusions: Study 1: Weight management interventions in adults with ID differ from recommended practice and further studies to examine the effectiveness of multi-component weight management interventions for adults with ID and obesity are justified. Study 2: The TAKE 5 weight maintenance intervention can effectively support adults with ID maintain their weight. Assessment of the cost effectiveness of the TAKE 5 weight management programme is justified. Study 3: The TAKE 5 multi-component weight loss intervention in its current structure can be equally effective for adults with ID as in adults without ID and obesity. A study with a larger sample could facilitate the identification of sociological and biological predictors for weight loss in adults with ID. Study 4: This study identified specific facilitators and barriers experienced by carers during the process of supporting obese adults with ID to lose weight. Future research could utilise these findings to inform appropriate and effective weight management interventions for individuals with ID.

A thesis submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy (Community Psychology), Department of Psychology in the Faculty of Arts at the University of Zululand, South Africa, 2013.
In recent years, significant attention has been given in the popular and academic press to an ‘obesity crisis’ that supposedly, is both ever increasing and sweeping across the world. The study was undertaken to explore the influence of wellness in weight loss. Although it is not known why the prevalence of obesity has increased so suddenly and markedly specifically in the past twenty years, experts agree that the rise is unlikely to be related to a sudden shift in genetic or biological factors within the individual. The causes are largely environmental or a consequence of the mismatch between our physiology and an environment where food is abundant and physical activity unnecessary. Moreover, there seems to be an increasing belief that psychological instability and childhood experiences play a great role in this epidemic. The present study focused on the influence of wellness in weight loss. The holistic approach to deal with this study was undertaken looking at mental, physical and spiritual wellness. Specifically the study looked at food or diet (healthy food and nutrition as important in promotion of good health), fitness or exercise, meditation (helps reduce stress), mental or emotional health and community (social isolation leads to severe stress, which in turn may result in unhealthy behaviour). The results were interesting in that, there was a significant loss of weight amongst the participants at the end of the study; participants demonstrated a positive change and displayed willingness to take better care of their selves to stay well. Qualitatively, participants reported an increase in daily physical activities, healthier dietary choices, feelings of optimism and greater self acceptance. Thus wellness shows promise as a weight loss intervention.

This dissertation provides an ethical justification of surgical weight loss interventions for the treatment of obesity. Situating obesity as not merely a public health concern but also fundamentally a problem of clinical medicine confronting individual patients and physicians, the dissertation argues that the time frame of public health interventions is too long for individuals presently facing obesity and its deleterious physical and social co-morbidities. It argues that failure to address weight loss on an individual level, and specifically to consider the clinical appropriateness of weight loss surgery (WLS), raises serious questions about failure to respect autonomy and promote patient welfare. Moreover, social skepticism or rejection of WLS as a treatment option raises concerns about fairness, as this failure indicates that obesity is not regarded in relevantly similar ways to other life-threatening and health-impairing conditions.

The dissertation examines various reasons that obesity and its myriad interventions, including WLS, are inadequately addressed in the clinical setting. It argues that considerations with cultural and ethical valence play a critical role in obesity's different and unfair treatment within clinical medicine. Gendered and theologically informed attributions of blame, self-blame, shame, and self-stigma influence the attitudes and actions of both patients and clinicians with regard to addressing obesity. Inappropriate and conceptually confused ascriptions of responsibility impede social acceptance of, and access to, WLS. The dissertation's criticism and subsequent reconceptualization of these ascriptions of responsibility from a perspective informed by feminist epistemology and ethics provide the foundation upon which to consider reform of current clinical practices surrounding treatment of obesity. This dissertation concludes that WLS is both ethically and clinically justified.

Background: Malnutrition and the cachexia syndrome are common in people with cancer. A combination of reduced nutritional intake and abnormal metabolism can lead to physical and psychological disturbances which may impair quality of life and reduce survival. Improved patient outcomes are more likely if treatments and nutritional support can be initiated before significant weight loss has occurred. Methods: A three phase, mixed methods study was undertaken. The primary aim was to gain a greater understanding of the complex factors that have an effect on, and can predict, weight loss in people with cancer. Phases I and II involved the psychometric testing of the Cancer Appetite and Symptom Questionnaire (CASQ). The instrument was tested for reliability among patients receiving radiotherapy (n=34). Predictive validity of the CASQ, using ROC curve analysis, was determined in patients with lung or upper GI cancer (n=185). Total CASQ scores (possible range, 0 to 48) were assessed at baseline, together with percentage weight change after 3 months. An exploratory qualitative study, following the principles of grounded theory, was conducted to explore the causes and influencing factors on weight change. Results: When tested for reliability, the intra-class correlation coefficient of the CASQ was 0.80 (95% CI 0.68 to 0.92) and the difference between total CASQ scores at the two time points was -0.20 (95% CI -1.21 to 0.80). The optimum cut point of the total CASQ score to predict >5% weight loss was 31/32 (C statistic = 0.64; sensitivity 65%, specificity 62%, PPV 33%, NPV 86%), and to predict >10% weight loss was 29/30 (C statistic = 0.75; sensitivity 71%, specificity 66%, PPV 19%, NPV 95%). Exploratory modelling using multiple linear regression techniques suggested that BMI, MUST score, age and the CASQ items of enjoyment of food and pain, were most predictive of weight loss. Nine patients with lung or upper GI cancer and three carers participated in semi-structured interviews. Analysis of the data confirmed the vulnerability of this patient group in terms of symptom burden and nutritional risk. From the findings, a conceptual model that explains the influences on weight change in people with cancer was proposed. Conclusions: Patients with lung and upper GI cancer are at high risk of malnutrition. Psychometric testing of the CASQ suggests that the instrument can predict weight loss in this patient group. Due to the low PPV, further refinements are needed before the instrument is able to be used in clinical practice. A conceptual model which explains the complex process of influences on weight change in people with cancer can improve knowledge and understanding, ultimately informing healthcare practice.

Obesity continues to be a major cause of morbidity and mortality and worldwide prevalence rates continue to rise. The cornerstone for treating obesity remains diet and lifestyle, with the ultimate goal being normalising those parameters that are associated with ill health, for example hyperinsulinaemia and insulin resistance. Because obesity predominantly develops due to a mismatch between energy intake and utilisation, this thesis looked at the effects of dietary interventions upon Resting Energy Expenditure (REE) and substrate oxidation. In addition, the impact of popular dietary interventions upon body composition and insulin resistance was examined. When phenotypic characteristics were investigated before and after weight loss by using hypocaloric diets, which differed in fat and carbohydrate content, Fat-Free Mass (FFM) and Fat Mass (FM), were strong predictors of REE before and after the intervention and weight loss rather than the specific dietary intervention, significantly predicted post intervention REE. Fasting fat oxidation was found to be lower in obese subjects and they had a lower postprandial response to a high fat challenge. This implied that a diet high in fat is more likely to promote a positive energy balance an ultimate weight gain. The final study compared 4 popular dietary interventions. Each was equally effective at achieving clinically significant weight loss and improvements in insulin sensitivity. Although none was significantly more superior, there was a trend supporting three of the diets (Atkins’, Weight Watchers and Rosemary Conley) above the other (Slim-Fast) and it was the pattern of weight loss, i.e. mainly loss of FM, which proved beneficial with regards to improving insulin sensitivity. In summary, this thesis confirms that REE is mainly predicted by FFM and FM and that there is diminished fat oxidation on obese subjects. What this thesis also adds to previous research that it if a specific diet can improve the pattern of weight loss, this can be clinically beneficial.

This thesis describes the results of dietetic led weight management for weight loss in three different groups of subjects: overweight; overweight with angina; and those whose body weight was close to the healthy upper BMI of 25 kg/m2. It forms part of a growing literature examining moderate weight loss as a success outcome in weight management. The work in this thesis addresses an important general research question; whether the effect of modest weight loss per se on established risk factors for IHD was similar across a number of subject groups. The specific aims were to examine the effect of moderate weight loss on the established IHD risk factors, fibrinogen, factor VII activity, plasma and whole blood viscosity, PAI activity and t-PA antigen. The role of modest weight loss on the adrenal hormone DHEAS was also studied. The conclusion of this thesis is that modest weight loss, (around 4%) which can be achieved through well planned dietetic management, does produce important reductions in IHD risk. The weight loss achieved was similar in groups with BMI > 28 kg/m2, with or without IHD, but less in absolute terms in individuals with baseline weights near the top of the healthy (acceptable range). Reductions in factor VII activity and RCA were related to the amount of weight loss, but the reductions were not greater in those with higher baseline values and existing IHD. The falls in factor VII activity and RCA were accompanied by falls in other established IHD risk factors, plasma lipid concentrations and blood pressure.

Introduction: There is proven therapeutic benefit in bariatric surgery for obese patients. Consequently the National Institute of Clinical Excellence UK has provided referral guidelines for bariatric surgery. Successful bariatric surgery will result in massive weight loss and ptotic skin, which can cause significant functional and psychological problems. As the number of cases of bariatric surgery increases, a corresponding number of massive weight loss patients will require plastic surgery. In this novel field of post massive weight loss surgery there is a lack of understanding of the demographics, physical symptoms and psychological health of this new group of patients. The tools to assess them are few and not validated, the patient pathway is disjointed and there is no consensus on standardised provision. Method: A prospective multicentre, observational study of outcomes in 100 patients undergoing bariatric and post massive weight loss plastic surgery at 2 clinical sites was performed. Each patient followed a standard operating protocol. This included undergoing a semi structured interview, completing five patient-report outcome measures, having anthropometric measurements and clinical photographs taken. Conclusion: This observational study identified key psychosocial themes prevalent in massive weight loss patients, during their weight loss journey. It identified there are no validated patient reported outcome measures available specific to this cohort of patients. This work led to the development of a new validated tool for massive weight loss body contouring.

The research was performed to determine factors associated with weight loss maintenance. Factors examined included: a) physical characteristics, b) eating habits, c) self-motivation level and d) activity level. Subjects included 19 overweight females who had participated in a nutrition and exercise program held at Virginia Polytechnic Institute and State University. Two separate groups of subjects were contacted and interviewed. Group 1 (n=11) participants in a six week treatment program, consisting of a very low calorie (530 kcal) liquid diet, and a supervised exercise program corresponding to 60% VO₂ max for 30-40 min., 3 times/week. Group 2 ( n=8) consisted of an eight week treatment program, consisting of mild caloric restriction (1200-1500 kcal/day), and a supervised exercise program corresponding to 70% VO₂max for 30-40 min. Group 1 was 12 months post formal treatment and group 2 6 months. A questionnaire was developed and administered to the subjects. The first three sections were multiple choice concentrating on eating habits, behavior modification techniques, and self-motivation level (SMI). The last section was an interview session ascertaining information on activity levels. Of the factors examined, four were found to be prevalent for both groups: skipping breakfast and a strong appetite in the evening showed higher average weight gains, preplanning meals and higher self-motivation levels produced a lower average weight gain. Group 1 showed lower average weight gains for those individuals who joined another program and ate 3 meals a day. Group 2 showed individuals who had higher activity levels had lower average weight gains. Due to the low incidence of maintenance of weight loss, it appears necessary to emphasize maintenance strategies during treatment sessions. Also it appears necessary to individualize treatment for subjects due to the range of self-motivation levels. Booster sessions and/or continued treatment may be helpful for those exhibiting a low motivation trait.
M.S.

Objective: The purpose of this study was to determine the extent to which the presence of social support correlates with attempts at weight loss in the past 12 months, attempts not to gain weight in the past 12 months, and participants’ satisfaction with their weight status. Methods: We used a cross-sectional study design using data collected by the 2003-2004 and 2005-2006 National Health and Nutrition Examination Surveys (NHANES) (CDC). For this study we included males and females, of multiple ethnicities, and a range of ages from 40 to 70 + years. Participants with missing data on height and weight were not included in the study. The final sample consisted of 3,982 participants. We defined social support using three domains: affiliation with religious organizations, relationships of trust, and social participation (Irwin J, et al., 2008). Weight loss attempts, weight maintenance attempts, and satisfaction were defined based on self-report. Analysis: We analyzed different classifications of social support in relation to three separate weight loss variables. The measure of association was an odds ratio. Logistic regression models provided odds ratios adjusted for potential confounders. All analyses were conducted in SUDAAN version 10 (RTI, Research Triangle Park, NC) to account for the complex survey design. Conclusion: Social support was not associated with weight loss variables. Various reasons for these results could include the age of the participants or the lack of questioning into the intensity of the social support being received.

Bariatric surgery, also known as weight loss surgery (WLS) is an intervention for individuals who are suffering from obesity and weight-related health complications which often accompany being 100 pounds or more overweight (Smith et al., 2011). Even though bariatric surgery has been shown to be a life-saving and life-enhancing operation, efforts to seek out surgery options, qualify and prepare for the procedure, recover from surgery, and then adapt new routines to support surgery are challenging not only for the patient, but also for the people with whom the patient spends the most time—their romantic partners (Applegate & Friedman, 2008; Bylund, Benzein, & Carina, 2013; Moore & Cooper, 2016; Sarwer, Dilks, & West-Smith, 2011). This dissertation was a means to explore relational, food, and WLS success experiences that take place within couples when at least one person has had bariatric surgery. Comparisons between life before, during, and after WLS were discussed with focused attention given to relationship dynamics and daily food routines (Bocchieri, Meana, & Fisher, 2002). The couple’s definition of WLS success and the means by which they have been successful were launching points for more in-depth conversation. Data was generated through 2 interviews per couple (n = 11) with patients who met selection criteria for the study—committed long-term relationship and of the same residence for at least the past 5 years with at least 1 person having been successful with WLS. Success was defined by the WLS patient, however they had to be at least 2 years post-WLS, the critical time period where postoperative weight regain has been shown to occur, in order to participate (Magro et al., 2008; Ogden, Avenell, & Ellis, 2011; Pories et al., 2016). A thematic analysis with multiple rounds of coding was conducted after data saturation was met and couples indicated their agreeableness with results through a short, follow-up survey which also functioned as a form of member-checking. Overall, couples’ relationship dynamics were characterized as secure and WLS gave them another way to give support, engage in teamwork, and ultimately become closer. Patients and spouses explained that they loved each other unconditionally, no matter what the patient weighed, and this had been the reality for their entire relationship. Thus, security was the theme for relationship dynamics with support, teamwork, and closer as subthemes. Spouses expressed their desire to help the WLS patient when it came to being open to change and then making necessary modifications in habits and lifestyle. The commitment to change happened before WLS and a mind-shift happened after WLS that enabled both people to adjust their thinking, consistently evaluate their routines, and continue to change their behaviors. As a result, commit and mind-shift were the themes and subsequent changes (diet, exercise, and mindsets) were the subthemes. A secure relationship and commitment to making “better choices” assisted the patient in experiencing WLS success and this meant that their spouse experienced success, too; “it’s our success together.” The theme for WLS success was follow-through and subthemes were results, comfort, happy, and freedom. Hope was also a by-product of success and it was the grand-theme of this study.

Despite the increasing prevalence of obesity and the array of treatment modalities available, maintenance of reduced-weight in the long-term is uncommon. The reason(s) why weightregain is so commonplace remains contentious. The primary purpose of this dissertation was to determine the extent to which weight-loss in obese adults, when the intervention included an optimal exercise prescription, resulted in adaptations that may be considered aberrant and reflect risk of weight-regain. Unique to this investigation was the multifactorial approach to addressing the issue of adaptation through consideration of metabolic, physiological, and psychosocial factors. Accurate body composition assessment is a fundamental requirement upon which evaluation of adaptation to weight-loss is based. An additional purpose of the dissertation was to evaluate multi-frequency bioelectrical impedance analysis (MFBIA) as a technique for use in assessing body composition change of obese adults during weight-loss. Further, optimal weight management requires an incorporation of effective exercise prescription. Therefore, a final aim of the dissertation was to determine the optimal exercise intensity for weight management. Together the goals of this thesis were addressed through a series of studies, the first three relate to use of bioelectrical impedance analysis; the fourth and fifth studies were associated with exercise prescription for obese adults; and the final study, incorporating three components, dealt with adaptation to weight-loss in the obese. In the first study, twenty-nine young healthy adults, 17 males and 12 females (mean± SEM; 21.8 ± 0. 7 yrs and 20.3 ± 0.3 yrs) were recruited to assess the technical reliability (i.e., interinstrument and inter-operator reliability) of three MFBIA monitors. Technical reliability was assessed for both errors of measurement and associated analyses. In addition, intra-operator and intra-instrument variability was evaluated for repeat measures over a 4-hour period. The measured impedance values from a range of resistance-capacitance circuits were accurate to within 3 percent of theoretical values over a range of 50- 800 ohms. Similarly, phase was measured over the range 1 degrees-19 degrees with a maximum deviation of 1.3 degrees from the theoretical value. The extrapolated impedance at zero frequency was equally well determined (+/-3 percent). However, the accuracy of the extrapolated value at infinite frequency was decreased, particularly at impedances below 50 ohms (approaching the lower limit of the measurement range of the instrument). The inter-instrument/operator variation for whole body measurements were recorded on human volunteers with biases of less than +/-1 percent for measured impedance values and less than 3 percent for phase. The variation in the extrapolated values of impedance at zero and infinite frequencies included variations due to operator choice of the analysis parameters but was still less than +/-0.5 percent. The second study investigated the effect of moving from standing to lying supine on blood and plasma volumes, serum electrolyte concentrations, and measurements of whole-body impedance using MFBIA over a 60 minute period in 12 subjects (8 males, 4 females) 26.7 ± 5.5 yrs, 172.3 ± 6.9 em, and 71.0 ± 7.7 kg. While no significant differences were found in serum sodium, chloride or potassium concentrations as a function of the posture change, estimates of both blood and plasma volumes increased during the 60 minutes spent supine. Blood volume increased by 10.5 (4.2 to 16.4)percent and plasma volume increased 10.5 (5.0 to 17.6)percent. Similarly, whole-body resistivity measured at 50 kHz increased significantly by 24.1 (6.3 to 36.5) Q in absolute values across the hour supine, with the measurement at 60 minutes reflecting a 4. 7 ( 1.3 to 6. 7)percent increase in resistivity from the baseline measure. Although the weight lost across the hour was only 0.11 (0.05 to 0.15) kg, the change in total body water estimated from resistivity measures is likely to be significantly larger. The results from this study reflect the need for implementation of a standardised preparatory rest time prior to taking BIA measurements, and demonstrate the limitations associated with a single frequency, whole-body approach for assessing body-fluid distribution. The purpose of the third study was to validate the use of MFBIA to determine change in body composition of obese adults during weight reduction by direct comparison with total body water as measured by stable-isotope dilution. Specifically, the study had three parts. Firstly, from the data obtained on the total sample at baseline, the aim was to develop a prediction equation for the estimation ofTBW from MFBIA. The second aim was to validate the prediction equation in a subsample during (wk-5) and after the completion of a 12-wk weight-loss intervention. The final aim of the study was to determine whether intervention type influenced the accuracy of TBW predicted by MFBIA. Multiple regression analysis revealed that the MFBIA-derived prediction equation prior to weight-loss was able to determine TBW with a SEE of 1.9L by combining the impedance index (Ht2/R10o), age, gender, and body weight. However, during weight-loss, the comparison of TBW predicted by MFBIA and measured with deuterium dilution had a much larger bias than after completion of the weight-loss intervention. It was further revealed that the magnitude of the bias was influenced by the intervention mode, with those individuals on a very-low-energy diet recording greater measurement bias. These results raise concern for the accuracy of MFBIA during periods of weight-loss in obese adults. In particular, weight-loss elicited through severe restriction in dietary intake appears most problematic. In contrast, the post-intervention TBW measures determined from the MFBIAequation derived at baseline had a mean difference of only 0.9L relative to the group mean derived by deuterium dilution. Further, using the impedance index alone post-intervention, the mean TBW measures were within 0.5L of the mean reference measure. In the fourth study the relative and absolute levels of exercise intensity corresponding with the lactate threshold (LT) and ventilatory threshold (Tvent) were determined in forty-two sedentary obese adults, 23 females and 19 males (42.9±1.8 yrs; 36.8±0.9 kg.m-2 ). Subjects were obese but otherwise healthy and taking no medication known to modifY heart rate. Subjects were required to attend a testing session each week for three weeks scheduled for the same time of day, and day of the week. The three sessions involved: (1) a treadmill test to assist in subject familiarisation. The test enabled researchers to gauge working capacity and enable subjects to become accustomed with the treadmill and gas analysis apparatus; (2) a discontinuous graded treadmill test to assess cardiorespiratory function; and (3) assessment of body composition and resting metabolic rate. On two separate occasions subjects undertook a discontinuous graded treadmill walking test consisting of 4-minute work stages separated by 2-minute rest periods. During the last 30 seconds of each work stage, subjects rated perceived exertion (RPE) using the Borg 6-20 scale. Immediately on completion of each work stage, duplicate blood samples were collected by finger prick, haemolysed in 1 OO)ll of chilled perchloric acid, and stored for later blood lactate analysis. Throughout both tests HR was recorded and respiratory gases were collected and analysed. Resting metabolic rate was assessed by indirect calorimetry using a ventilated hood system. The major finding of this study was that corresponding with LT and Tvent respectively, the relative intensities defined as percentV02R (63.4±1.4 percent; 63.8±1.8 percent), percent HRR (65.2±1.6 percent; 66.6±1.5 percent) and percent HRpeak (78.2±1.0 percent; 79.2±1.0 percent), and the absolute intensity defined by METs calculated physiologically would be categorised as "hard" by the current guidelines. In contrast, at L T and T vent the relative intensity defined by RPE (12.6±0 .2; 12.8±0.3), and absolute intensity defined by METs calculated from mechanical parameters (4.8±0.2; 5.0±0.2), fall into the "moderate" intensity category. Therefore, there is a need to redefine the descriptors of exercise intensity for the obese population. Further, linear regression analysis revealed a relatively strong negative relationship (r=-0.58, P<0.001) between HRLT and age , and the addition of gender to the regression analysis improved the strength of the prediction equation (HRLr = 145.6- 0.623* Age(yrs) + 9.824*Gender (M=l, F=2) r=-0.70, P<0.001). Importantly, the intensity thresholds tested were at a level well tolerated by the obese population, and considered to be of moderate intensity. The purpose of the fifth study was to identify optimal aerobic exercise intensity for obese adults and to compare this with the relative and absolute intensity categories outlined in current guidelines provided by the Surgeon General (U.S. Dept. HHS, 1996) and American College of Sports Medicine (ACSM, 1995; 1998). In particular, the equivalence between submaximal markers of exercise intensity, challenged recently in studies of trained and recreational athletes and chronic obstructive pulmonary disease sufferers, was evaluated for the first time in obese adults. Using a testing procedure outlined in Study 4, data was assessed from 32 obese adults (15 males and 17 females), 42.1 ± 1.7 yrs and 37.4 ± 1.0 kg.m-2. The study showed that in the obese [1] the percent HRpeak-percent V02peak relationship was significantly greater than ACSM recommendations; [2] the percent HRR was equivalent with percent V02R not percent V02peak; and [3] exercise prescription at fixed percentages of V02peak or HRpeak corresponded with wide ranges of exercise intensities in relation to LT. These results together with those from Study 4 demonstrated for the first time that current exercise prescription guidelines for the obese are too conservative, particularly where optimising the exercise-induced benefits for weight management are concerned. The final study was based upon the hypothesis that weight-regain is attributed more to behavioural adaptations than to compensatory metabolic processes. The purpose of this randomised-control intervention was to ascertain the extent to which metabolic, physiological, and psychosocial factors adapt in obese adults during a period of weight decrement. Additionally, it was hypothesised that metabolic adaptation is related to the rate of weight-loss, the mode facilitating the energy deficit responsible for the weight-loss, and the tissue composition of the weight that is lost. In particular the study goal was to determine what evidence there is that loss of body weight results in metabolic, physiological, or psychosocial adaptations that are aberrant. Forty-eight obese adults (22 males and 26 females) on average 42.9 ± 1.8 years, 107.2 ± 3.4 kg, and 36.8 ± 0.9 kg.m-2 were recruited. Subjects were matched for gender, age, and BMI before being randomly assigned to very-low-energy diet plus exercise (VLED+Ex), low-fat diet plus exercise (LF+Ex), or control (C) groups. In the first two weeks, subjects undertook two treadmill tests to determine cardiorespiratory capacity and the relationship between submaximal markers of exercise intensity at increasing workloads. In the third week, all subjects underwent testing of baseline measures of resting metabolic rate, body composition, thyroid hormone function, blood lipid profile, body satisfaction and self-reported health. After this period, subjects followed the VLED+Ex, LF+Ex or C program for the following 12 weeks. For VLED+Ex and LF+Ex body composition and metabolic measures were repeated after the 4th and 8th week of the intervention. All measurements were repeated in the week following completion of the intervention, week 16 of the study program. Forty-two subjects completed the 16-week study. Collectively, the results from the weight-loss intervention do not support the notion that weightloss in obese adults results in aberrant changes in metabolic, physiological or psychosocial variables that would in turn place the reduced-obese adult at risk of weight regain. In particular, perception of size for both males and females post-intervention was strongly related with body weight (r = 0.71 and r = 0.89 for males and females respectively), relative weight (r = 0.81, r = 0.86), and BMI (r = 0.81, r = 0.84). While positive correlations were found between the magnitudes of change in body size and body satisfaction, self-reported health improved and limitations to daily physical activity were reduced in both intervention groups when compared with the control group at the completion of the intervention period. Overall, there was no evidence with respect to psychosocial factors that the intervention and concomitant change in body size was perceived negatively, and in many respects the greater the change in body size the greater the perceived benefit. In terms of physiological adaptation, participation in 12 weeks of aerobic endurance and resistance weight training was positively reflected in improvements in cardiorespiratory fitness, with an average improvement in maximal aerobic capacity (L.min-1 ) of 17.7 percent and 13.1 percent in the VLED+Ex and LF+Ex groups respectively. The energy-cost of exercise at LT did not change significantly with weight-loss and thus exercise prescribed at LT for the reduced-obese adult would as effective for increasing energy expenditure through physical activity as was shown at baseline. Although not reaching statistical significance, the time required to expend the energy suggested as necessary for weight maintenance was reduced by an average of 9 percent and 8 percent in the VLED+Ex and LF+Ex groups respectively. In terms of metabolic adaptation, the findings were somewhat conflicting depending upon the manner of comparing energy expenditure in people before and after a change in body size. Data was analysed via four different statistical approaches cited in the literature. Analysis of covariance with FFM (the variable most strongly explaining the variance in RMR measures) as the covariate revealed no significant differences in RMR between groups at any time point during the study. Comparing the actual RMR-FFM regression lines for each group before and after the intervention revealed that the slopes and intercepts of the RMR-FFM relationships did not alter significantly after weight-loss. In contrast, the third and fourth series of analyses in which predicted and observed measures ofRMR were compared pre and post intervention, and the change in FFM related to change in resting oxygen consumption were compared, were conflicting. However, it was proposed that these somewhat conflicting results may be explained by the influence of the energetic contribution of organ tissue to total FFM energetics. As would be expected, during the intervention changes in RQ reflected the nature of the dietary intervention. However, unexpectedly at the completion of the intervention the group that lost weight most rapidly had an RQ that was not significantly different from the values at baseline. The findings do not support the notion purported by previous research that weight-loss, and in particular rapid weight-Joss, increases the reliance on carbohydrate oxidation in the reduced-obese state and thus increasing the risk of weight regain. It may be concluded from the RMR and RQ data that as a function of endurance exercise training the adverse consequences cited in studies where weight is lost through dietary restriction alone are ameliorated. Finally, the VLED+Ex group had significantly reduced concentrations offT4, T4, T3 and IT3 at the completion of the intervention relative to baseline. However, the change in hormone concentration was not related to the change in body weight or FFM for any of the hormones. Further, all subjects were euthyroid throughout the intervention. Therefore, while rapid weightloss results in statistically significant reductions in thyroid hormones, determining whether this reflects clinically significant and persistent down-regulation of endocrine function, and thus reduced metabolic potential, requires further investigation.

This review discusses popular diet methods that are advertised as effective options for people struggling to lose weight. Obesity is a prevalent issue in the United States, which increases a person's risk for other comorbidities, notably cardiovascular diseases. This review seeks to determine the most effective weight loss method by comparing Orlistat, meal replacement products, Medifast, and bariatric surgery. The studies selected included both male and female adults (18+ years old) classified as overweight or obese based on their body mass index (BMI). The results showed that each of the four methods caused weight loss, but not all sustained this weight loss. Bariatric surgery had the highest percentage weight loss for patients, which was often sustained for many years after the procedure due to the physiological manipulation of the digestive system. Though bariatric surgery had the most promising results, not everyone qualifies for the procedure based on their BMI and other comorbidities. Thus, a more feasible weight loss and maintenance plan is the Medifast program. This paid program includes pre-made meals and the option of one-on-one counseling to implement lifestyle changes that can be used long-term for sustained, healthy weight loss.

Thesis (Ph. D.)--Missouri University of Science and Technology, 2008.
Vita. The entire thesis text is included in file. Title from title screen of thesis/dissertation PDF file (viewed August 28, 2008) Includes bibliographical references (p. 77-80).

Obesity is one of the most serious health problems facing modern society and strategies to address this pandemic have so far been ineffective. Although weight loss (WL) is achievable, prevention of weight regain is a major challenge. The overall aim of this thesis was to identify predictors of WL and weight loss maintenance (WLM) to promote better tailored and sustainable interventions. A systematic review evaluated the evidence from 80 studies examining predictors of WL and/or WLM in behavioural and/or dietary WL interventions (with or without exercise) in overweight and obese individuals. Aside from physiological factors such as initial weight loss, a number of personal characteristics broadly conceptualised as reflecting affective, cognitive, behavioural and motivational factors were acknowledged as potential predictors of WL and/or WLM. Affective (e.g. anxiety), behavioural (e.g. eating behaviour, self-monitoring, social support, physical activity, treatment adherence, previous WL attempts) and motivational factors (e.g. self-efficacy) were the strongest predictors identified. Study 1 assessed predictors of WL and WLM in free-living participants (N=71) who received healthy eating advice with (HE+F) or without (HE) advice to increase dietary fibre. Predictors of WL were age, body weight and body image at baseline (affective), fasting plasma leptin and disinhibition (behavioural) with some differences according to diet group. These also predicted WLM at 1 month follow-up. At 12 month follow-up, having a higher body weight at week 12 and greater depression (affective) at follow-up were associated with greater weight regain. Additionally, having stronger beliefs that medical reasons cause obesity (cognitive) and less stressful life events (affective) were associated with better WLM. Study 2 utilised an online survey and cluster analysis to examine affective, cognitive, behavioural and motivational factors in a real world setting with individuals (N=314), who had previously attempted to lose weight using different WL methods. Two distinct clusters were identified: less successful (Cluster 1) and more successful (Cluster 2). Cluster 2 was associated with lower emotional and external eating, lower disinhibition and higher restraint (behavioural), less depression, anxiety and stress (affective), and significantly higher diet satisfaction, eating self-efficacy (motivational) than Cluster 1. Study 3 examined predictors of WL in an NHS delivered 12 week community based weight management programme (N=22). Higher diet satisfaction, an improvement in body image and higher baseline body weight were significant predictors of WL. Based on the evidence presented in this thesis, there are clear personal characteristics which promote and sustain obesity. WL and WLM is clearly not just a problem of appetite control. Affective (stressful life events, body image, diet satisfaction and depression), behavioural (eating behaviour) and motivational factors (self-efficacy and motivation) were the most consistent psychological predictors of WL and/or WLM across all studies. Interventions should therefore target these personal characteristics in order to promote WL and prevent weight regain. The paucity of studies incorporating long-term follow-up shows that further research is needed to examine the role of affect, cognition, behaviour and motivation in the long term. A multidisciplinary approach to tackle obesity, which addresses psychological, social, environmental, and biological factors is essential to ensure comprehensive care, best practice and outcomes.

The present study used healthy questionnaires to evaluate the compounding effects of weight loss and weight gain in choosing to exercise. The questionnaire was distributed to 31 participants via social media outlets. Demographic information was also recorded such as height, weight, ethnicity, and income. The height and weight recorded was used to correlate the BMI with the AUC values. This data did not show a strong correlation between body mass index with high or low AUC values, these values were evenly distributed between underweight, normal/average weight, and overweight participants. . The questionnaires designed to assess how people view exercise and to determine if there is a pattern with sequencing delays with the calculated switch point and AUC. Statistical and visual analyses were conducted at the group and participant level. The switch points, were documented from each delay and was calculated to determine the compounding sequence that was preferred from each participant. The results from the study indicated that participants chose to exercise immediately within the first day, when the consequence was to lose weight. The results for the gain condition indicated that participants would gain weight instead of exercise, to a certain limit (100 days), when they chose to then engage in exercise behavior regularly. The conclusion of this study shows that the longer the delay the less valued the outcome is. This is important when understanding the obesity epidemic within the United States.