EXS - Teses de Doutoramento
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- Tigh composition, cardiorespiratory fitness and physical activity in a weight loss program with overeight and obese womenPublication . Martins, Sandra Cristina Ribeiro Vaz da Silva; Sardinha, Luís Fernando Cordeiro BettencourtThe purpose of the present Thesis was to analyze thigh composition through body composition methods and alterations research areas and its associations with cardiorespiratory fitness (CRF) and physical activity (PA) in overweight and obese premenopausal women. Three studies were conducted within the PESO program (Promotion of Execise and Health in Obesity), a behaviourally-based intervention with a strong emphasis on PA and nutrition. Study I developed and validated predictive equations for thigh composition assessment, using computed tomography (CT) as the reference method and with dual-energy X-ray absorptiometry (DXA) and anthropometry indicators as prediction models. Study II aimed the cross-sectional analysis of the associations between CRF and daily PA with thigh composition volumes determined by CT. In Study III a longitudinal approach allowed the investigation of the effects of a weight-loss intervention on thigh composition, CRF, and daily PA. Key results show that: a) prediction equations for the different thigh components may be useful in different settings where body composition may be critical and need to be followed longitudinally, such as in wasting illnesses; b) women with higher levels of CRF presented greater thigh skeletal muscle mass, independently from their PA level; c) greater low intensity PA was associated with lower thigh subcutaneous adipose tissue; d) maximal oxygen consumption level is associated with different thigh composition phenotypes; e) a 16-month weight-loss intervention positively impacted thigh low density SM tissue area, along with a decrease in low density SM quality and increases in CRF, and daily PA, suggesting the occurrence of the athlete’s paradox in overweight and obese premenopausal women; f) beneficial changes were observed from 0-16 months in body composition determined by CT, DXA and anthropometry indicators simultaneously with improvements in CRF and in habitual PA.
- The biological variability of body composition of children and adolescent athletes engaged on different sportsPublication . Quitério, Ana Luísa Dias; Sardinha, Luís Fernando Cordeiro BettencourtThe chemical maturity does not occur until postpubescence is reached, and in young athletes, due to the biological phenomena occurring with exercise, there are dynamic fluctuations of body components beyond the natural growing process. The use of multi-component models is recommended instead of two-component approaches, dividing body weight into body fat and FFM. The limitations of body composition methods that do not account for the variability of the FFM may be also partially overcome by using age- and gender-specific constants of FFM components, although among young athletes, there is lack of these specific constants. The current dissertation assembled data of young Portuguese athletes, aged 8-18 years. Overall, it was demonstrated that: 1)the specific constants of FFM hydration developed by Lohman provide valid total body water estimates; 2)muscle mass can be accurately predicted using newly developed anthropometric equations; 3)there is a dose-dependent relationship between weekly training hours and molecular and cellular components, above 9 hrs/wk, independently of sports; 4)bone and lean mass molecular components are associated with participation in anaerobic and high impact sports, while body cell mass is related with an aerobic and non-gravitational sport; 5)young male competitive swimmers do not differ from non-athletic age-matched controls in bone mineral status.
- Predictors of exercise adherence and weight control : an application of self-determination theoryPublication . Silva, Marlene Nunes; Teixeira, Pedro Jorge do Amaral de Melo; Matos, Maria Margarida Nunes Gaspar deThe present Thesis was set within a longitudinal randomized controlled trial, consisting of a 1-year theory-based behavior change intervention and a 2-year follow-up period with no intervention. This trial included 239 overweight or obese women (age: 37.6±7 y; BMI: 31.5±4.1 kg/m2) who were premenopausal and free from identified disease. The main intervention was designed to increase physical activity and internal motivation, following self-determination theory (SDT). While tested before for other health behaviors with promising results, SDT had never been previously applied to weight management in longterm, controlled designs. Thus, the four studies comprising this Thesis were designed to provide a comprehensive analysis of how a theory-based intervention, implemented to affect specific theory-based mediators, would impact exercise adherence and body weight change both in short and long-term, from a SDT perspective. After a complete description of the study protocol, theoretical framework, and main intervention strategies (study 1), study 2 showed that the intervention was successful in affecting theory-driven mediators, physical activity, and weight change at 12 months (intervention’s end), demonstrating that the socio-contextual characteristics advanced by SDT Abstract -2- are amenable to manipulation, and revealing the potential utility of SDT to shape behavioral interventions targeting the promotion of physically active lifestyles and weight-change. Studies 3 and 4 searched for a more in-depth understanding of the dynamics of exercise motivation by exploring and testing mediational models aimed at outlining theory-based mechanisms and their impact on different types of physical activity at intervention’s end (study 3), and on long-term behavioral exercise regulations and physical activity (24-month) and 36-month weight change (study 4). Convergent with previous research, but extending it into the context of a randomized controlled trial, these studies indicated that perceived needsupportive health care climate, psychological needs for autonomy and competence, and intrinsic motivation mediate the effects of the experimental treatment climate on structured exercise behavior. Furthermore, these variables rested within the causal path of long-term weight loss, providing evidence from a link between experimentally-increased autonomous motivation, long-term physical activity adoption, and 3-year weight management. This application of SDT to physical activity and weight management provides experimental evidence that an autonomy-supportive context facilitates the internalization of regulatory processes, particularly through its effect on exercise-related constructs, which in turn promote long-term positive behavioral and clinical outcomes in overweight/obese women.
- Preditores psicossociais, exercício físico e sucesso num programa de controlo do pesoPublication . Palmeira, António João Labisa da Silva; Teixeira, Pedro Jorge do Amaral e MeloO presente trabalho teve como objectivo analisar varáveis psicossociais e associadas ao exercício como preditoras de sucesso num programa comportamental de tratamento do excesso de peso e obesidade. Para tal, realizaram-se 4 estudos com base no Programa PESO (Promoção do Exercício na Saúde e Obesidade), uma intervenção de longo prazo em mulheres pré-menopáusicas com excesso de peso ou obesidade. No estudo I o objectivo foi analisado sob a perspectiva dos paradigmas sócio-cognitivos de modificação comportamental. No estudo II avaliou-se prospectivamente as associações entre as alterações a curto prazo na imagem corporal, qualidade de vida e bem-estar subjectivo e as alterações no peso a curto e a longo prazo. O estudo III analisou as associações entre estas variáveis e a prática regular de exercício físico. O estudo IV aferiu se as alterações no peso e nas variáveis de imagem corporal, qualidade de vida, bem-estar subjectivo se influenciavam reciprocamente, num papel duplo de mediador e resultado, proporcionador do sucesso no programa. Efectuaram-se ainda trabalhos complementares que suportaram a produção dos estudos principais. Os principais resultados revelaram que: a) a auto-eficácia e a imagem corporal são variáveis essenciais para a compreensão dos processos de perda do peso; b) existem efeitos recíprocos entre as alterações no peso e na imagem corporal; c) os resultados no peso são pressagiados por alterações a curto prazo na auto-estima e perturbação emocional (bem como na imagem corporal); e d) a actividade física regular está associada aos melhores resultados no peso, na qualidade de vida e no bem-estar subjectivo. Os estudos permitem concluir que os tratamentos comportamentais para a obesidade devem incluir conteúdos que promovam a auto-eficácia e a auto-estima e melhorem a imagem corporal e vivência emocional, bem como contemplar avaliações regulares destas variáveis. Por último, a inclusão da actividade física e exercício regular nestes programas pode e deve ser considerada um elemento potenciador das melhorias destas variáveis. Por último, a inclusão da actividade física e exercício regular nestes programas pode e deve ser considerada um elemento potenciador das melhorias destas variáveis e não apenas como um mecanismo de aumento do dispêndio calórico.
- Body Composition and metabolic syndrome features in overweight and obese womenPublication . Rocha, Paulo Manuel Espadinha Pinheiro da; Sardinha, Luis Fernando Cordeiro BettencourtThis thesis sought to analyze the relationships between body composition markers and metabolic syndrome features in overweight and obese women, being structured in three scientific problems. The first scientific problem investigated the separate contributions of waist and hip circumference to proinflammatory and atherothrombotic metabolic syndrome disturbances. Associations of thigh adipose and muscle tissue compartments with metabolic features were also studied. For a given waist circumference, a larger hip circumference predicted a lower diabetogenic and atherothrombotic risk. Femoral-gluteal adipose tissue seems to mediate this protective role. The second problem studied the independent associations of abdominal and thigh adipose tissue compartments with metabolic syndrome clinical features. Contrarily to visceral adipose tissue, a larger thigh subcutaneous adipose tissue was related with a lower thrombotic and atherogenic risk. The last problem analyzed the independent relations of abdominal and thigh adipose tissue compartments with liver fat. The associations of proinflammatory and atherothrombotic risk factors with liver fat were also studied. Thigh subfascial adipose tissue was inversely associated with liver fat, suggesting that this thigh fat depot may play a protective role against ectopic liver fat storage. An abdominal obesity phenotype associated with a diabetogenic, inflammatory, and atherothrombotic metabolic profile may to contribute to liver lipotoxicity.
- Weight-loss in overweight and obese women : models and methods to assess body composition changesPublication . Minderico, Cláudia Sofia Ferreira Correia; Sardinha, Luis Fernando Cordeiro BettencourtThis thesis derives from three scientific problems which resulted in the same number of scientific articles. The background and questions of this investigation are centre in the methodological area and body composition rules. The first problem analysed the accuracy of some laboratory and field methods available (DXA, BIA and Anthropometry) in assessing body composition changes in overweight and obese women after a 16 months weight loss program management using a four-component molecular model as reference. The second studied the reasons why the changes in weight and body composition may result in functional changes in the thoracic gas volume (VTG) and, consequently, in the inadequate assessment of fat mass through a two-compartment model as Bod Pod. The last problem tested the accuracy of Bod Pod in tracking body composition changes using DXA as reference. It was verified that the single frequency BIA-Tanita device, a field method, showed a good level of performance in tracking body composition changes, similarly to the laboratory methods used, DXA and Bod Pot, despite being a two-compartment model. Draw attention to those different methods should not be applied in different moments interchangeably to detect body composition changes after a weight loss program.
- Biological variability in human body composition : implication in the rules and methodology research areasPublication . Silva, Analiza Mónica Lopes de Almeida; Sardinha, Luis Fernando Cordeiro Bettencourt; Heymsfield, StevenThis thesis presents five investigations related to the body composition rules and methodology research areas. In the rules, newly developed methods such as in vivo neutron activation analysis are used as the reference to evaluate the assumption of the stable mineral-to-protein density in Siri's three-compartment model for estimating total-body-fat mass. In the methodology area, the assessment of extracellular water (ECW) with a dilution method and whole-body counting showed significant differences in the fluid distribution-age relations among race groups, with the largest age-related differences observed in African American subjects. In addiction, normative values using a recently developed statistical technique for testing the significance of conditioning variables to generate equations for the 10th, 25th, 50th, 75th and 90th percentiles of ECW were developed. The remaining investigations deal with the evaluation and calibration of body composition methods. Hence,widely used methods, such as dual-energy x-ray absorptiometry (DXA) and air displacement plethysmography in fat mass assessment, were compared with a reference multicompartmental molecular model in a adolescent athletic population. Finally, calibration models were developed for bone mineral content, lean soft tissue, and fat mass filling a methodological gap in the DXA system when subjects taller than DXA scan area need to be evaluated.