Weight-loss in overweight and obese women : models and methods to assess body composition changes

Doutoramento em Motricidade Humana, na especialidade de Saúde e Condição FísicaThis 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.Esta tese é constituída por 3 problemas científicos que deram origem ao mesmo número de artigos científicos. As questões e fundamentos desta tese centraram-se na área metodológica e nas regras da composição corporal. O primeiro problema analisou a validade de alguns dos métodos laboratoriais e de terreno disponíveis (DXA, BIA e Antropometria) na medição das alterações da composição corporal durante um programa de 16 meses de perda de peso apenas em mulheres usando, como referência, um modelo 4-C. O segundo problema estudou as razões pelas quais as alterações no peso e na composição corporal podem resultar em alterações funcionais no volume do gás toráxico (VGT) e, consequentemente, na inadequada avaliação da massa gorda através do método de 2-C com Bod Pod. O último problema testou a validade do Bod Pod para detectar alterações da composição corporal usando como referência o DXA. Verificou-se que o método de terreno de bio-impedância de frequência única, BIA-Tanita, teve um elevado desempenho na detecção das alterações da composição corporal, similar às técnicas laboratoriais utilizadas, DXA e Bod Pod, apesar de ser um modelo de dois compartimentos. De salientar que as técnicas utilizadas nos diferentes momentos devem ser sempre as mesmas.FC

Os efeitos do conflito e do enriquecimento entre o trabalho e a família no bem-estar dos trabalhadores na adultez emergente e na adultez

Tese de mestrado, Psicologia (Secção de Psicologia dos Recursos Humanos, do Trabalho e das Organizações), Universidade de Lisboa, Faculdade de Psicologia, 2018O presente estudo tem como principal objetivo analisar os efeitos do conflito trabalho-família (CTF) e do enriquecimento trabalho-família (ETF) no bem-estar dos trabalhadores, assim como o papel moderador das diferentes fases do ciclo de vida nessas mesmas relações. Os dados foram obtidos através de uma amostra de trabalhadores portugueses (N = 1144) de uma consultora e de um banco. Os resultados evidenciam a existência de uma relação positiva entre o CTF e o burnout, bem como a existência de uma relação positiva entre o ETF e o engagement. Mais, a relação entre o CTF e o burnout não apresenta diferenças entre a amostra de indivíduos em fase de adultez emergente e a amostra de indivíduos em fase de adultez. No que concerne à relação entre o ETF e o engagement, esta é mais forte na fase de adultez emergente. Os resultados obtidos contribuem para a literatura ao reforçarem a existência de uma relação entre o CTF e o burnout e, por outro lado, entre o ETF e o engagement, salientando a pertinência das teorias sobre o CTF e o ETF se ajustarem às fases do ciclo de vida. Neste estudo são apresentadas algumas implicações práticas, bem como limitações e sugestões para estudos futuros.The aim of the present study is to analyze the effects of work-family conflict (WFC) and work-family enrichment (WFE) on employees’ well-being, as well as the moderating role of the different life cycle stages in these relations. The data was gathered through a sample of Portuguese employees (N = 1144) from a consultant and a bank. The results support the existence of a positive relationship between WFC and burnout, as well as the existence of a positive relationship between WFE and engagement. Moreover, the relationship between WFC and burnout doesn’t present differences between the early adulthood and the adulthood stages. Furthermore, the relationship between WFE and engagement is stronger in the early adulthood stage. The results contribute to the literature by reinforcing the existence of a relationship between WFC and burnout, as well as between WFE and engagement, emphasizing the relevance of life cycle stages regarding these relationships. Some practical implications, as well as limitations and suggestions for future studies are presented

Linking cardiorespiratory fitness classification criteria to early subclinical atherosclerosis in children

It is unclear if cardiorespiratory fitness (CRF) can be used as a screening tool for premature changes in carotid intima-media thickness (cIMT) in paediatric populations. The purpose of this cross-sectional study was 3-fold: (i) to determine if CRF can be used to screen increased cIMT; (ii) to determine an optimal CRF cut-off to predict increased cIMT; and (iii) to evaluate its ability to predict increased cIMT among children in comparison with existent CRF cut-offs. cIMT was assessed with high-resolution ultrasonography and CRF was determined using a maximal cycle test. Receiver operating characteristic analyses were conducted in boys (n = 211) and girls (n = 202) aged 11-12 years to define the optimal sex-specific CRF cut-off to classify increased cIMT (≥75th percentile). Logistic regression was used to examine the association between the CRF cut-offs with the risk of having an increased cIMT. The optimal CRF cut-offs to predict increased cIMT were 45.81 and 34.46 mL·kg(-1)·min(-1) for boys and girls, respectively. The odds-ratios for having increased cIMT among children who were unfit was up to 2.8 times the odds among those who were fit (95% confidence interval: 1.40-5.53). Considering current CRF cut-offs, only those suggested by Adegboye et al. 2011. (Br. J. Sports Med. 45(9): 722-728) and Boddy et al. 2012 (PLoS One, 7(9): e45755) were significant in predicting increased cIMT. In conclusion, CRF cut-offs (boys: ≤ 45.8; girls: ≤ 34.5 mL·kg(-1)·min(-1)) are associated with thickening of the arterial wall in 11- to 12-year-old children. Low CRF is an important cardiovascular risk factor in children and our data highlight the importance of obtaining an adequate CRF.info:eu-repo/semantics/publishedVersio

Cross-sectional and prospective impact of reallocating sedentary time to physical activity on children's body composition.

BACKGROUND: The amount of time children spend in sedentary behaviours may have adverse health effects. OBJECTIVE: To examine the substitution effects of displacing a fixed duration of sedentary time with physical activity (PA) on children's body composition. METHODS: We included 386 children (197 boys). Outcomes were body mass index, waist circumference, total body fat mass and trunk fat mass assessed by dual-energy X-ray absorptiometry. Sedentary time and PA were measured with accelerometers. Data were analysed by isotemporal analyses estimating the effect of reallocating 15 and 30 min d-1 of sedentary time into light (light physical activity), and moderate-to-vigorous (MVPA) PA on body composition. RESULTS: Reallocating 15 and 30 min d-1 of sedentary time into MVPA was negatively associated with body fatness in cross-sectional analyses. Prospectively, reallocating 30 min of sedentary time into 30 min of MVPA was negatively associated with waist circumference (β = -1.11, p  0.05) with body fatness outcomes. CONCLUSIONS: Substituting sedentary time with MVPA using isotemporal analysis is associated with positive effects on body composition.The study was supported by the Portuguese Foundation of Science and Technology. Support/grant: PTDC/DES/108372/2008

The predictive role of raw bioelectrical impedance parameters in water compartments and fluid distribution assessed by dilution techniques in athletes

The aims of this study were to analyze the usefulness of raw bioelectrical impedance (BI) parameters in assessing water compartments and fluid distribution in athletes. A total of 202 men and 71 female athletes were analyzed. Total body water (TBW) and extracellular water (ECW) were determined by dilution techniques, while intracellular water (ICW) was calculated. Fluid distribution was calculated as the ECW/ICW ratio (E:I). Phase angle (PhA), resistance (R) and reactance (Xc) were obtained through BI spectroscopy using frequency 50kHz. Fat (FM) and fat\u2010free mass (FFM) were assessed by dual\u2010energy X\u2010ray absorptiometry. After adjusting for height, FM, FFM, age and sports category we observed that: PhA predicted ICW (females: \u3b2 = 1.62, p < 0.01; males: \u3b2 = 2.70, p < 0.01) and E:I (males and females: \u3b2 = 120.08; p < 0.01); R explained TBW (females: \u3b2 = 120.03; p < 0.01; males: \u3b2 = 120.06; p < 0.01) and ECW (females: \u3b2 = \u20130.02, p < 0.01; males: \u3b2 = 120.03, p < 0.01) and ICW (females: \u3b2 = \u20130.01, p < 0.053; males: \u3b2 = \u20130.03 p < 0.01); and Xc predicted ECW (females: \u3b2 = 120.06, p < 0.01; males: \u3b2 = 120.12, p < 0.01). A higher PhA is a good predictor of a larger ICW pool and a lower E:I, regardless of body composition, age, height, and sports category. Lower R is associated with higher water pools whereas ECW expansion is explained by lower Xc. Raw BI parameters are useful predictors of total and extracellular pools, cellular hydration and fluid distribution in athletes

Visceral Abdominal and Subfascial Femoral Adipose Tissue Have Opposite Associations with Liver Fat in Overweight and Obese Premenopausal Caucasian Women

Abdominal obesity has been associated with liver fat storage. However, the relationships between other body composition depots and metabolic syndrome features with hepatic fat are still unclear. We examined abdominal and thigh adipose tissue (AT) compartments associations with liver fat in 140 overweight and obese premenopausal Caucasian women. Blood lipids and, proinflammatory and atherothrombotic markers associations with hepatic fat were also analyzed. A larger visceral AT (VAT) was related with liver fat (P < 0.05). Contrarily, thigh subfascial AT was inversely related to liver fat (P < 0.05). Increased fasting insulin, triglycerides, PAI-1 concentrations, and a higher total-cholesterol/HDL-cholesterol ratio were also associated with hepatic fat, even after adjustment for VAT (P < 0.05). Thigh subfascial adiposity was inversely associated with liver fat, suggesting a potential preventive role against ectopic fat storage in overweight and obese women. These results reinforce the contribution of an abdominal obesity phenotype associated with a diabetogenic and atherothrombotic profile to liver lipotoxicity

Predictors of Psychological Well-Being during Behavioral Obesity Treatment in Women

This study examined the association of autonomy-related variables, including exercise motivation, with psychological well-being and quality of life, during obesity treatment. Middle-aged overweight/obese women (n = 239) participated in a 1-year behavioral program and completed questionnaires measuring need support, general self-determination, and exercise and treatment motivation. General and obesity-specific health-related quality of life (HRQOL), self-esteem, depression, and anxiety were also assessed. Results showed positive correlations of self-determination and perceived need support with HRQOL and self-esteem, and negative associations with depression and anxiety (P < .001). Treatment autonomous motivation correlated positively with physical (P = .004) and weight-related HRQOL (P < .001), and negatively with depression (P = .025) and anxiety (P = .001). Exercise autonomous motivation was positively correlated with physical HRQOL (P < .001), mental HRQOL (P = .003), weight-related HRQOL (P < .001), and self-esteem (P = .003), and negatively with anxiety (P = .016). Findings confirm that self-determination theory's predictions apply to this population and setting, showing that self-determination, perceived need support, and autonomous self-regulation positively predict HRQOL and psychological well-being

Predicting short-term weight loss using four leading health behavior change theories

<p>Abstract</p> <p>Background</p> <p>This study was conceived to analyze how exercise and weight management psychosocial variables, derived from several health behavior change theories, predict weight change in a short-term intervention. The theories under analysis were the Social Cognitive Theory, the Transtheoretical Model, the Theory of Planned Behavior, and Self-Determination Theory.</p> <p>Methods</p> <p>Subjects were 142 overweight and obese women (BMI = 30.2 ± 3.7 kg/m²; age = 38.3 ± 5.8y), participating in a 16-week University-based weight control program. Body weight and a comprehensive psychometric battery were assessed at baseline and at program's end.</p> <p>Results</p> <p>Weight decreased significantly (-3.6 ± 3.4%, p < .001) but with great individual variability. Both exercise and weight management psychosocial variables improved during the intervention, with exercise-related variables showing the greatest effect sizes. Weight change was significantly predicted by each of the models under analysis, particularly those including self-efficacy. Bivariate and multivariate analyses results showed that change in variables related to weight management had a stronger predictive power than exercise-specific predictors and that change in weight management self-efficacy was the strongest individual correlate (p < .05). Among exercise predictors, with the exception of self-efficacy, importance/effort and intrinsic motivation towards exercise were the stronger predictors of weight reduction (p < .05).</p> <p>Conclusion</p> <p>The present models were able to predict 20–30% of variance in short-term weight loss and changes in weight management self-efficacy accounted for a large share of the predictive power. As expected from previous studies, exercise variables were only moderately associated with short-term outcomes; they are expected to play a larger explanatory role in longer-term results.</p

Who will lose weight? A reexamination of predictors of weight loss in women

BACKGROUND: The purpose of this study was to analyze pretreatment predictors of short-term weight loss in Portuguese overweight and obese women involved in a weight management program. Behavioral and psychosocial predictors were selected a priori from previous results reported in American women who participated in a similar program. METHODS: Subjects were 140 healthy overweight/obese women (age, 38.3 ± 5.9 y; BMI, 30.3 ± 3.7 kg/m(2)) who participated in a 4-month lifestyle weight loss program consisting of group-based behavior therapy to improve diet and increase physical activity. At baseline, all women completed a comprehensive behavioral and psychosocial battery, in standardized conditions. RESULTS: Of all starting participants, 3.5% (5 subjects) did not finish the program. By treatment's end, more than half of all women had met the recomended weight loss goals, despite a large variability in individual results (range for weight loss = 19 kg). In bivariate and multivariate correlation/regression analysis fewer previous diets and weight outcome evaluations, and to a lesser extent self-motivation and body image were significant and independent predictors of weight reduction, before and after adjustment for baseline weight. A negative and slightly curvilinear relationship best described the association between outcome evaluations and weight change, revealing that persons with very accepting evaluations (that would accept or be happy with minimal weight change) lost the least amount of weight while positive but moderate evaluations of outcomes (i.e., neither low nor extremely demanding) were more predictive of success. Among those subjects who reported having initiated more than 3–4 diets in the year before the study, very few were found to be in the most successful group after treatment. Quality of life, self-esteem, and exercise variables did not predict outcomes. CONCLUSIONS: Several variables were confirmed as predictors of success in short-term weight loss and can be used in future hypothesis-testing studies and as a part of more evolved prediction models. Previous dieting, and pretreatment self-motivation and body image are associated with subsequent weight loss, in agreement with earlier findings in previous samples. Weight outcome evaluations appear to display a more complex relationship with treatment results and culture-specific factors may be useful in explaining this pattern of association

Specific Bioelectrical Impedance Vector Analysis Identifies Body Fat Reduction after a Lifestyle Intervention in Former Elite Athletes

Background: specific bioelectrical impedance vector analysis (BIVA) has been proposed as an alternative bioimpedance method for evaluating body composition. This investigation aimed to verify the ability of specific BIVA in identifying changes in fat mass after a 16-week lifestyle program in former athletes. Methods: The 94 participants included in the Champ4life project (clinicaltrials.gov: NCT03031951) were randomized into intervention (n = 49) and control (n = 45) groups, from which 82 athletes completed the intervention (age 43.9 ± 9.2 y; body mass index 31.1 ± 4.6 kg/m2). Fat mass was estimated by dual-energy X-ray absorptiometry. Bioelectric resistance, reactance, phase angle, and vector length were assessed by bioelectric impedance spectroscopy, and the BIVA procedure was applied. Results: A significant (p &lt; 0.05) group x time interaction for fat mass, specific resistance, reactance, and vector length was found. Fat mass and vector length significantly (p &lt; 0.05) decreased in the intervention group, while no change was measured in the control group. Considering the participants as a whole group, changes in vector length were associated with changes in fat mass percentage (r2 = 0.246; β = 0.33; p &lt; 0.001) even after adjusting for age, sex, and group (R2 = 0.373; β = 0.23; p = 0.002). Conclusions: The specific BIVA approach is suitable to track fat mass changes during an intervention program aimed to reduce body fat in former athletes