本研究的目的在於以電阻抗法測定的脂肪比例作為標準，評價各種兒童肥胖定義診斷脂肪過量時的診斷準確性。爲了達到這項研究目的，本研究分為三個部份。首先，研究的第一部份評價了生物電阻抗法（Bio-electrical impedance analysis, BIA）在測量中國兒童青少年身體成份時的效度。隨後，幾種被廣泛應用的電子脂肪磅測量身體脂肪比例時的測量準確度被進行了評價。最後，在大規模人群測試中，利用精確的電子脂肪磅及幾種人體測量學指標決定的脂肪水平，不同兒童肥胖定義的診診斷脂肪過量的斷準確性被進行了評價。共有255名9至19歲的中國兒童青少年參與了第一和第二部份的測試，利用雙能X光骨密度儀（Dual-energy X-ray absorptiometry, DEXA）測量的體成份作為標準，比較了通過標準電阻抗法以及幾種被廣泛電子脂肪磅測量而來的體成份。研究結果顯示，生物電阻抗法是測量中國兒童青少年體成份有效的方法，然而，所有以前研究發展的BIA預測方程均未能準確估計受試者的去脂體重（Fat-free mass, FFM）。四種商業電子脂肪磅在測量受試者的體脂有類似的診斷準確度。隨後，另外的2,134名兒童青少年參與了本研究第三部份的測試，利用經過第二部份經過調整的脂肪磅測量受試者的體脂比例，同時測量人體測量學指標。研究結果發現，現有關於兒童肥胖的定義在診斷香港兒童、青少年脂肪過量的診斷準確性不夠。此外，受試者工作特徵曲綫分析（Receiver operating characteristics, ROC）發現利用基於身高和體重的指數來定義兒童肥胖在診斷肥胖兒童時較基於腰圍的指數有更好的敏感度和特異性。因此，研究者可以通過調整這些身高和體重的指數的劃分點來獲得對兒童肥胖更好的診斷準確性。 / 研究一（第3章）的目的在於評價生物電阻抗（Bio-electrical impendence analysis, BIA）方法在預測中國兒童青少年的去脂體重（Fat-free mass, FFM）中的效度，同時，也驗證已有的利用BIA方法發展的方程預測中國兒童、青少年FFM的效度。共有255名9-19歲健康的中國兒童、青少年（127名男生、128名女生）自願參與此次測試。利用傳統的單頻（50 kHz）的手腳電阻抗儀測試人體的電阻與電抗。利用雙能X光骨密度儀（Dual-energy X-ray absorptiometry, DEXA）作為測量FFM的標準。以DEXA測試的FFM為標準，對24個已有的BIA預測FFM的方程進行交互驗證。研究結果顯示，在本研究的人群中，利用24個已有的BIA預測方程所預測FFM與DEXA測量而來FFM高度相關。然而，這24個方程都未能準確預測本研究測試人群中由DEXA測量而來的FFM。利用多元線性回歸及交互驗證的方法，本研究發展了一個預測中國兒童、青少年FFM的預測方程：FFM (kg) = 1.613 + 0.742 × 身高(cm)²/電抗 (Ω) + 0.151 × 體重 (kg); R² = 0.95; SEE = 2.45kg; CV = 6.5%。本研究的研究結果表明，已有的BIA預測FFM的方程均不能通過交互驗證，從而準確的預測本研究人群的FFM。利用本研究人群發展而來的BIA預測FFM的方程，對預測中國兒童、青少年的FFM有良好的效度。本研究證明利用BIA方法可以準確的預測中國兒童、青少年的體成份。 / 研究二（第4章）旨在驗證4種利用BIA原理發展而來的商業電子脂肪磅在測量中國兒童、青少年體脂比例時的效度，以及判斷這些脂肪磅診斷身體脂肪過量時的診斷表現。參與研究一的255名中國兒童、青少年也參與本研究。利用DEXA作為測量體成份的標準測量。同時，4種電子脂肪磅（Model A, Biodynamics-310; Model B, Tanita TBF-543; Model C, Tanita BC-545 和 Model D, InBody 520）利用製造商內置的BIA方程測量受試者的體成份。研究結果表明，採用製造商內置的BIA方程測量體脂比例時，在男性中，Model B和Model C測量的體脂比例與DEXA測量的體脂比例有明顯差異 （p < 0.05）；Model C低估了脂肪過量兒童、青少年在在受試人群中的百分比（X²=10.714, p=0.001）。在女性中，Model B、Model C和Model D測量的體脂比例與DEXA測量的體脂比例有明顯差別，脂肪過量兒童在占受試人群中的比例被這三種脂肪磅所低估。由於在這四種脂肪磅和DEXA測量的%BF有著較高的相關性，回歸分析被用於調整這四種脂肪磅所測量的體脂比例。在調整后，在男性和女性中，所有調整的脂肪磅測試的體脂比例與DEXA測量的體脂比例之間沒有分別。在男性和女性受試者中，卡方檢驗結果顯示，所有校正的脂肪磅診斷的脂肪過量兒童、青少年占受試人群中的比例與DEXA的診斷比例之間沒有發現明顯區別。 此外，在女性中，與未校正的脂肪磅的對脂肪過量兒童、青少年診斷的敏感度比較，調整后的Model B 和 ModelC 脂肪磅對脂肪過量的兒童診斷的敏感度得到明顯改善 (Model B, X²=9.818,p=0.002; Model C, X²=4.615, p=0.032)。本研究的研究結果建議在利用電子脂肪磅內置方程測量中國青少年、兒童的體脂比例時，其效度需要進行驗證。因為在脂肪磅和DEXA測量之間有較高的相關性和較小的偏差，經調整的脂肪磅可以用於在進行大規模人群測試時，測量中國青少年、兒童的體脂比例，以及作為對脂肪過量兒童、青少年的診斷工具。 / 研究三（第5章）的目的在於調查基於身高體重的指數和基於腰圍的指數在診斷香港兒童、青少年脂肪過量時的總體診斷表現；以及判斷現有兒童肥胖定義診斷香港兒童、青少年脂肪過量時的診斷表現。共有來自香港多所中小學的2134名9-19歲的受試者，包括1135名男性、999名女性參與本研究。利用研究二調整的便攜式足對足電子脂肪磅測量受試者的體脂比例。基於體脂比例的兒童肥胖，即脂肪過量，被定義為體脂比例在男性高於25%，女性高於30%。四種基於BMI的兒童肥胖定義、兩種基於香港數據利用腰圍對兒童肥胖的定義、以及香港現有的兒童肥胖定義用於此研究。受試者工作特徵曲綫分析（Receiver operating characteristics, ROC）被用於分析身高體重指數（BMI）、標準身高體重（PWH）、腰圍（WC）和腰圍身高比（WHtR）在診斷香港兒童、青少年脂肪過量時的總體診斷表現。診斷試驗的指標被用來判斷現有兒童肥胖的定義診斷香港兒童、青少年脂肪過量時的診斷表現。本研究發現，在男性中，BMI、PWH、WC和WHtR在診斷香港兒童、青少年脂肪過量時有相同的良好的診斷表現[受試者工作特徵曲綫下面積(area under the curve of ROC, AUC) = 0.909-0.923]。然而，在女性中，WC（AUC=0.840）和WHtR（AUC=0.850）診斷香港兒童、青少年脂肪過量時的診斷表現差於BMI（AUC=0.900）和 PWH （AUC=0.903）。此外，現有兒童肥胖定義在診斷香港兒童、青少年脂肪過量時診斷敏感度較低，敏感度在男性中為0.325-0.761；女性中為0.128-0.588。利用最好診斷準確度的方法來確定的BMI、PWH、WC和WHtR的劃分點在診斷脂肪過量時，在男性中有相似的診斷表現，診斷敏感度在0.816-0.868之間，診斷特異度在0.803-0.869之間；對於女性，BMI和PWH 較WC和WHtR有較高的敏感度和特異度。本研究的發現表明，在診斷脂肪過量時，基於身高和體重的指數總體診斷表現好於基於腰圍的指數；現有兒童肥胖定義在診斷香港兒童、青少年脂肪過量時的診斷表現不佳。進一步，通過調整以身高和體重為基礎指數的劃分點可以使其在診斷脂肪過量時有更好的診斷表現。 / The purpose of this study was to evaluate the diagnostic accuracy of various childhood obesity definitions using bioelectrical impedance analysis (BIA) as a criterion measure of body fat. To achieve such an objective, the study involved three phases. First, the validity of BIA in measuring body composition in Chinese children and adolescents was evaluated. Then, examination on measuring accuracy of several popular BIA scales was performed. Finally, mass testing of body fat levels using an accurate BIA scale, as well as other anthropometric measures, was conducted to evaluate the diagnostic accuracy of childhood obesity definitions. A total of 255 healthy Chinese children and adolescents aged 9 years to 19 years participated in the first and second phases of the study. Body composition was measured from BIA using a criterion device (Biodynamics 310) and four popular commercial BIA scales and compared with measurements from dual-energy X-ray absorptiometry (DEXA). BIA provided excellent predictions of body composition among Chinese children and adolescents. However, all of the previously developed BIA equations yielded biased estimation. The four commercial BIA scales had similar diagnostic accuracy in measuring body fat. Subsequently, another 2,134 boys and girls were recruited to take part in body fat measurements using the best BIA scale identified in the second phase with adjusted equations, as well as other anthropometric measurements. The diagnostic accuracy of all existing definitions of childhood obesity was poor in both genders. Moreover, Receiver Operating Characteristics (ROC) analysis found that childhood obesity definitions using weight-and-height based indices [Body mass index (BMI) and weight-for-height) had superior sensitivity and specificity in identifying obese children compared with waist circumference-based indices. Therefore, with adjusted cut-off criteria for weight-and-height indices, the diagnostic accuracy of childhood obesity would be improved. / Study I : Validity of BIA method in predicting FFM / The first study (Chapter 3) aimed to examine the validity of the BIA method in predicting fat-free mass (FFM) in Chinese children and adolescents and of various published BIA equations in estimating FFM in this particular group. A total of 255 healthy Chinese children and adolescents (127 boys and 128 girls) aged 9 years to 19 years participated in this study. BIA variables (e.g., resistance and impedance) were measured at 50 kHz between the hand and foot using a traditional BIA device. The criterion of FFM measurement was also assessed using DEXA. FFM estimated from 24 published BIA equations were cross-validated against the criterion measure from DEXA. FFM estimated from the 24 published BIA equations yielded high correlations with the directly measured FFM from DEXA. However, none of the 24 equations was statistically equivalent with the DEXA-measured FFM. Using multiple linear regression and cross-validation against the DEXA measurement, an alternative prediction equation was developed as follows: FFM (kg) = 1.613 + 0.742 × height (cm)²/impedance (Ω) + 0.151 × body weight (kg); R² = 0.95; SEE = 2.45 kg; CV = 6.5%. None of the previously developed BIA equations was able to cross-validate the FFM estimates of the present sample. An alternative BIA equation, with evidence of validation and cross-validation, was thus proposed. The method based on the BIA principle provides a valid estimation of body composition among Chinese children and adolescents. / Study II: Validity of popular BIA consumer scales in measuring body fat / The second study (Chapter 4) examined the validity in measuring body fat and the diagnostic performance of four different consumer BIA scales. The 255 Chinese children and adolescents from the first study also participated in this study. DEXA was used as the criterion measurement for %BF, which was also assessed using four BIA scales [Model A (Biodynamics 310), Model B (Tanita TBF-543), Model C (Tanita BC-545), and Model D (InBody 520)]. The validity in measuring body fat and the diagnostic performance in screening excess body fat of these BIA scales was first examined. In boys, differences in %BF between Models B, C, and DEXA were significant (p < 0.05). In girls, significant differences in %BF were observed between Models B, C, D, and DEXA (p < 0.05). The prevalence of overfat in boys was underestimated by Model C (X² = 10.714, p = 0.001). For girls, the prevalence of overfat was underestimated in Models B, C, and D. Because of the high correlation between the BIA scales and DEXA (r = 0.770.94), regression analysis was used to adjust the BIA scales in measuring %BF in this sample. After adjustment, the paired t-tests did not show differences in %BF between the adjusted BIA scales and the DEXA measurement in both genders. All adjusted BIA scales except Model A in girls showed substantial agreement with the DEXA measurement. In addition, compared with overfat classification using DEXA measurement, X² test showed that the prevalence of overfat in the present samples was classified correctly by all adjusted BIA scales in both genders. Compared with the original BIA measurements, the use of the adjusted Models B and D offered significant improvements in sensitivity for girls. These findings suggest that the embedded equations in BIA scales should be validated in assessing body compositions among Chinese children and adolescents. The adjusted BIA scales can be used in large population surveys due to the high correlation and small mean bias between the BIA scales and the DEXA measurements. In conclusion, the adjusted BIA scales can serve as diagnostic tools to classify overfat Chinese children into relevant subgroups. / Study III: Diagnostic accuracy of definitions of childhood obesity / The third study (Chapter 5) aimed to investigate the diagnostic performance of weight-and-height-based indices and waist circumference (WC-based indices as diagnostic tests to screen excess body fat in Hong Kong children and adolescents and to investigate the diagnostic accuracy of existing definitions of childhood obesity in Hong Kong. A total of 2,134 participants (1,135 boys and 999 girls) were recruited from local schools. The adjusted foot-to-foot BIA scale (Model B) in the second study was applied to assess %BF. The criterion of childhood obesity (i.e., overfat) was defined as over 25%BF for boys and over 30%BF for girls. Childhood obesity was also determined from four BMI-based references, two WC-based references, and the 1993 HK reference. The diagnostic accuracy of the existing definition for childhood obesity in screening excess body fat was evaluated using diagnostic indices. The Receiver Operating Characteristics (ROC) analysis was used to evaluate the general performance of BMI, PWH, WC, and WHtR in detecting overfat. In boys, ROC analysis showed no significant difference among the four indices in screening overfat [(area under the curve of ROC, AUC) = 0.909-0.923]. In girls, BMI and PWH performed better in detecting overfat than WC and WHtR (AUC of BMI = 0.900; AUC of PWH = 0.903; AUC of WC = 0.840 and AUC of WHtR = 0.850). All definitions for obesity showed low sensitivity (boys, 0.325-0.761; girls, 0.128-0.588) in detecting overfat. Cut-offs derived for best accuracy showed similar diagnostic performance in each index in boys but not in girls. In boys, the cut-offs of BMI, WC, WHtR, and PWH can provide similar sensitivity (0.816-0.868) and specificity (0.803-0.869) in screening overfat. In girls, BMI and PWH can provide higher sensitivity and specificity than WC and WHtR. This study’s findings demonstrate that the diagnostic performance of all existing definitions for obesity is poorer than expected in both genders. BMI and PWH are superior to use as proxy measures in screening overfat among Hong Kong Chinese children and adolescents for both genders. Moreover, the diagnostic performance of these indices can be improved by adjusting the existing cut-offs. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Wang, Lin. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 166-197). / Abstract and appendixes also in Chinese. / ABSTRACT --- p.i / 摘要 --- p.v / ACKNOWLEDGEMENT --- p.ix / PUBLICATIONS --- p.xi / LIST OF TABLES --- p.xv / LIST OF FIGURES --- p.xvii / ABBREVIATIONS --- p.xviii / Chapter CHAPTER 1. --- INTRODUCTION --- p.1 / Chapter 1.1. --- Background --- p.1 / Chapter 1.2. --- Purposes and significance --- p.4 / Chapter 1.3. --- Operational definitions --- p.5 / Chapter 1.3.1. --- Childhood overweight and obesity --- p.5 / Chapter 1.3.2. --- Body composition --- p.6 / Chapter 1.3.3. --- Bioelectric impedance analysis (BIA) --- p.6 / Chapter 1.3.4. --- Validity --- p.6 / Chapter 1.3.5. --- Diagnostic performance --- p.6 / Chapter 1.4. --- Hypothesis --- p.6 / Chapter 1.5. --- Limitations --- p.7 / Chapter 1.6. --- Delimitations --- p.7 / Chapter CHAPTER 2. --- LITERATURE REVIEW --- p.9 / Chapter 2.1. --- The epidemic and health consequence of childhood obesity --- p.10 / Chapter 2.1.1. --- Prevalence of childhood obesity --- p.10 / Chapter 2.1.2. --- Health consequence of childhood obesity --- p.15 / Chapter 2.2. --- Contributors of Childhood obesity --- p.16 / Chapter 2.2.1. --- Genetics --- p.17 / Chapter 2.2.2. --- Dietary intake --- p.17 / Chapter 2.2.3. --- Physical activity --- p.18 / Chapter 2.2.4. --- Sedentary behaviors --- p.18 / Chapter 2.3. --- Definitions of overweight and obesity in children and adolescents --- p.19 / Chapter 2.3.1. --- General definition of obesity --- p.19 / Chapter 2.3.2. --- Definitions and prevalence of childhood obesity in different countries --- p.21 / Chapter 2.3.3. --- Methods and current practices for identifying childhood obesity --- p.21 / Chapter 2.4. --- Methods for assessing body composition --- p.42 / Chapter 2.4.1. --- Body composition models --- p.42 / Chapter 2.4.2. --- Measurements methods to estimate body composition --- p.44 / Chapter 2.4.3. --- Specific issues of body fat in childhood --- p.60 / Chapter 2.5. --- Diagnostic accuracy of different definitions of childhood obesity --- p.61 / Chapter CHAPTER 3. --- STUDY I: VALIDITY OF BIOELECTRICAL IMPEDANCE MEASUREMENT IN PREDICTING FAT-FREE MASS OF CHINESE CHILDREN AND ADOLESCENTS --- p.67 / Chapter 3.1. --- Introduction --- p.67 / Chapter 3.2.1. --- Participants --- p.69 / Chapter 3.2.2. --- Measurements --- p.70 / Chapter 3.2.3. --- Data reduction and statistic analysis --- p.72 / Chapter 3.3. --- Results --- p.78 / Chapter 3.3.1. --- Descriptive statistics --- p.78 / Chapter 3.3.2. --- Cross-validation of published BIA equations --- p.79 / Chapter 3.3.3. --- Development of alternative BIA equations --- p.84 / Chapter 3.4. --- Discussion --- p.86 / Chapter 3.5. --- Conclusion --- p.92 / Chapter CHAPTER 4. --- STUDY II: VALIDITY OF FOUR COMMERCIAL BIA SCALES IN MEASURING BODY FAT AMONG CHINESE CHILDREN AND ADOLESCENTS --- p.93 / Chapter 4.1. --- Introduction --- p.93 / Chapter 4.2. --- Methods --- p.97 / Chapter 4.2.1. --- Participants --- p.97 / Chapter 4.2.2. --- Anthropometrics measurement --- p.97 / Chapter 4.2.3. --- Measurement of body composition --- p.97 / Chapter 4.2.4. --- Statistical analysis --- p.99 / Chapter 4.3. --- Results --- p.102 / Chapter 4.3.1. --- Characteristics of participants --- p.102 / Chapter 4.3.2. --- Reliability of BIA analysis --- p.103 / Chapter 4.3.3. --- Comparison of measuring body composition between BIA commercial devices (manufacturers’ equations) and DEXA measurement-Step 1 --- p.103 / Chapter 4.3.4. --- Comparison of measuring body composition between BIA commercial devices (adjusted equations) and DEXA measurement-Step 2 --- p.110 / Chapter 4.4. --- Discussion --- p.116 / Chapter 4.5. --- Conclusion --- p.123 / Chapter CHAPTER 5. --- STUDY III: DIAGNOSTIC ACCURACY OF DIFFERENT DEFINITIONS OF CHILDHOOD OBESITY IN IDENTIFYING OVERFAT AMONG CHINESE CHILDREN AND ADOLESCENTS --- p.124 / Chapter 5.1. --- Introduction --- p.124 / Chapter 5.2. --- Methods --- p.126 / Chapter 5.2.1. --- Participants --- p.126 / Chapter 5.2.2. --- Anthropometrics measurement --- p.127 / Chapter 5.2.3. --- Body fat measurement --- p.127 / Chapter 5.2.4. --- Definition of excess fatness --- p.128 / Chapter 5.2.5. --- Classification of participants --- p.128 / Chapter 5.2.6. --- Data reduction and statistic analysis --- p.129 / Chapter 5.3. --- Results --- p.131 / Chapter 5.3.1. --- Characteristics of participants --- p.131 / Chapter 5.3.2. --- Age-adjusted correlation among the different indices of obesity --- p.133 / Chapter 5.3.3. --- Prevalence rates of overweight/obesity --- p.134 / Chapter 5.3.4. --- Diagnostic agreement in assessing excess fat between %BF and anthropometric-based definitions --- p.137 / Chapter 5.3.5. --- Sensitivity and specificity --- p.138 / Chapter 5.3.6. --- Diagnostic performance of anthropometric indices in assessing excess fat --- p.141 / Chapter 5.3.7. --- Cut-offs of the anthropometric indices for screening excess fat --- p.143 / Chapter 5.4. --- Discussion --- p.148 / Chapter 5.5. --- Conclusion --- p.157 / Chapter CHAPTER 6. --- GENERAL DISCUSSION AND CONCLUSION --- p.158 / REFERENCE --- p.166 / APPENDIX A --- p.198 / APPENDIX B --- p.202 / APPENDIX C --- p.204 / APPENDIX D --- p.206 / APPENDIX E --- p.210

Background: Obesity’s rapid growth and its serious consequences for public health, is assessed as one of the most serious public health challenges. In Sweden, the number of children with child obesity has duplicated in 15 years. Statistics reveals that approximately 4 to 5% of all children in Sweden suffer of obesity. As families and individuals themselves choose their diet, they need knowledge to make healthy choices for themselves and for their children. Parents are the primary source for communicating health information to their children and adolescents. Hence, there is a demand to improve the targeted information to parents. The risk of a child becoming overweight reduces the sooner parents embrace healthy habits. Purpose: The aim was to examine the experts' experiences and perceptions of how parents get and receive information about children's health with a focus on child obesity. Method: The study design was explorative with a qualitative approach. Ten interviews were conducted and used for qualitative content analysis, and basis for the presented results. Results: The analysis resulted in ten subcategories and four categories presented below. 1. To study the environment around the entire family, 2. That there is a interest by all to promote children’s health, 3. To personalize information, 4. What the information should discuss. The main result of this study reveals that expert´s perceived parents today are getting good information through actors like child health center (BVC) and the school, hence the parents interpreted as positive to information regarding their children's health. However, it stated that the experts' experienced barriers in the treatment of child obesity and lack of information about child obesity. These barriers highlighted to depend on both genetics and environment while lack emphasized to base on ignorance and prejudices from parents and other stakeholders. Conclusion: The experts perceived that parents were positive towards information about children's health, but sometimes less positive towards information regarding child obesity. In contrary, the experts conveyed that there were gaps in the information of child obesity from BVC, due to a lack of knowledge and prejudice of the BVC: s staff. The biggest barrier to treatment and prevention against child obesity mediated as the environment. Society needs to make changes by suggestion to remove extra prices on candy, and instead both offer and send out information about healthier options. Suggested strategies was to organize group meetings to help parents manage information about child obesity. Stakeholders like BVC and school could take healthlitteracy into count when providing information. / Bakgrund: Fetmans snabba ökning och dess allvarliga konsekvenser för folkhälsan, bedöms som en av de allvarligaste folkhälsoutmaningarna. I Sverige har antalet barn med barnobesitas fördubblats på 15 år. Statistik visar att ungefär 4 till 5 % av barn i Sverige lider av obesitas. Eftersom familjer och individer själva väljer sin kost behöver de kunskap att göra hälsosamma val till sig själva och sina barn. Föräldrar är den primära källan för att vidarebefordra hälsorelaterad information till sina barn. Med hänsyn till detta behöver den riktade informationen till föräldrar utvecklas. Risken att ett barn blir överviktig minskar ju tidigare föräldrar anammar hälsosamma vanor. Syfte: Att undersöka experters erfarenheter och upplevelser av hur föräldrar får och tar emot information om barns hälsa med fokus på barnobesitas. Metod: Studiens design var explorativ med en kvalitativ ansats. Tio intervjuer genomfördes och med en kvalitativ innehållsanalys som grund, kunde resultat presenteras. Resultat: Analysen resulterade i tio subkategorier och fyra kategorier som presenteras nedan. 1. Att se över miljön runt hela familjen, 2. Att det finns ett intresse hos alla att främja barns hälsa, 3. Att individanpassa informationen, 4. Vad informationen ska avhandla. Huvudresultatet av föreliggande studie var att experterna uppfattade att föräldrar idag får bra information via aktörer som barnavårdscentralen (BVC) och skolan, samt att föräldrarna upplevdes som positiva till information gällande deras barns hälsa. Dock framkom att experterna upplevde barriärer vid behandling av barnobesitas och brister vid information som handlade om barnobesitas. Dessa barriärer ansågs bero på både arv och miljö. Dessutom ansågs bristerna grundas i okunskap och fördomar hos föräldrar och andra aktörer. Slutsats: Experterna upplevde att föräldrarna var positiva till information gällande barns hälsa, men ibland mindre positiva till information om barnobesitas. Intervjuade parter förmedlade att det fanns brister i informationen om barnobesitas från BVC, beroende på brist på kunskap samt fördomar hos BVC:s personal. Den största barriären för behandling och förebyggande insatser mot barnobesitas ansågs vara miljön. Samhället behöver göra förändringar genom att förslagsvis ta bort extrapriser på godis, och istället både erbjuda och sända ut information om hälsosammare alternativ. Förslag på strategier var att anordna gruppträffar för att hjälpa föräldrar att hantera information om barnobesitas. Aktörer som BVC och skolan behöver ta hänsyn till hälsolitteracitet när de ger information.

African American (AA) women have the highest prevalence of obesity than other groups in the US making them disproportionately at high risk for chronic diseases associated with obesity such type 2 diabetes mellitus. Research has shown that stress may be a risk factor for obesity and that it may be more prevalent within AA women. The aim of this study was to identify if there is an association between psychological stress in AA women in the US and abdominal obesity (AO). A cross sectional study design was employed using secondary data from the 2011-2012 National Health and Nutrition Examination Survey (NHANES). There were 655 AA female participants included in the study sample. The exposure variable was psychological stress assessed by select questions from the NHANES survey. The outcome variable was AO measured by waist circumference. Logistic regression was used to examine the relationship between psychological stress and AO among AA women. The results of this study were that psychological stress was correlated with increased odds of AO upon adjusting for age, BMI, educational level and marital status (OR=1.192 95% CI 0.305 – 4.655). However, the association was not statistically significant. When examining the relationship between other covariates and AO, having a formal education and being a married woman were each found to be associated with decreased odds of AO. The results were not generalizable, but they suggest areas of promise in better understanding the impact of AO among AA women which could lead to targeted interventions to reduce this outcome in the population as well as others.

published_or_final_version / Medicine / Doctoral / Doctor of Philosophy

Quatre études de liaison génome entier ont mis en évidence une région commune de5,6 Mb dans la région du chromosome 5q15 liée à des traits associés à l’obésité, cette région incluant le gène de la prohormone convertase 1 (PCSK1). Une mutation Pc1 chez la souris a été associée à l’obésité, l’hyperphagie et à une augmentation de l’efficacité du métabolisme. La déficience complète en PCSK1 a été associée à une forme récessive rare d’obésité chezl’homme, et depuis 1997 seuls trois patients présentant cette déficience ont été décrits dans la littérature. Les porteurs de mutations délétères PCSK1 présentent des phénotypes sévères,incluant l’obésité, des hypoglycémies post-prandiales et des problèmes intestinaux ethormonaux. Contrairement aux observations faites chez la souris, les membres des famillesporteurs hétérozygotes ont été considérés comme cliniquement sains. Toutes ces études ontdésigné PCSK1 comme un gène candidat important pour l’obésité.Dans un premier temps, la contribution du gène PCSK1 au risque d’obésitépolygénique a été évaluée chez 13,659 individus d’origine européenne issus de huit cohortescas contrôles ou familiales indépendantes. Neuf variants fréquents couvrant 92% de lavariabilité génétique du locus ont été génotypés. Les méta-analyses des huit études pour levariant commun rs6232 et pour le cluster rs6234-rs6235 ont montré une associationreproductible avec l’obésité chez l’adulte et chez l’enfant (P=7.27x10-8 et P=2.31x10-12respectivement). Le rs6232 était associé à une augmentation du risque d’obésité de 34%, alorsque le cluster rs6234-rs6235 augmentait le risque d’obésité de 22%. Les analysesfonctionnelles ont montré une diminution significative de 10,4% de l’activité catalytique de laprotéine PC1/3 pour le N221D, et une diminution non significative de l’activité catalytique dela protéine PC1/3 pour le cluster Q665E/S690T.L’implication du gène PCSK1 dans l’obésité monogénique a ensuite été entreprise parle séquençage des exons de PCSK1 chez 845 sujets obèses non-consanguins d’origineeuropéenne,. Huit nouvelles mutations non-synonymes ont été identifiées. L’étude des conséquences fonctionnelles des mutations détectées sur la protéine PC1/3 a montré que62.5% de ces mutations détectées étaient prédites délétères par les analyses in silico et 87.5%de ces mutations avaient un effet sur l’auto-activation ou sur l’activité enzymatique de PC1/3in vitro. Dans le but d’estimer le degré de pénétrance pour ces sept mutations pathogéniques,6,060 obèses et 6,274 sujets minces ont été génotypés, démontrant un enrichissement par sixde ces mutations PCSK1 chez les sujets obèses (P=0.007). Cette étude a mis en évidence pourla première fois une augmentation du risque d’obésité chez les porteurs hétérozygotes de mutations perte de fonction du gène PCSK1, confirmant un mode de transmission codominantde l’obésité avec une pénétrance incomplète. La pénétrance de l’obésité a été105estimée à 54.5% pour les porteurs hétérozygotes de mutations délétères PCSK1. Unedéficience partielle en PCSK1 pourrait expliquer environ 0.83% des formes extrêmesd’obésité et représenter la seconde forme la plus fréquente d’obésité monogénique après ladficience en MC4R.Pour conclure, en plus des formes syndromiques très rares d’obésité dues à unedéficience complète en PCSK1, ce travail a permis de démontrer le rôle des variants codantsfréquents non-synonymes dans le risque d’obésité, ainsi que l’importance longtempsinsoupçonné d’une déficience partielle en PCSK1 dans les formes monogéniques d’obésité. / Four whole genome studies basing on positional cloning approach revealed a region ofchromosome 5q linked to traits related to obesity, this region contained the gene coding forthe prohormone convertase 1 named PCSK1. Pc1 mutation in mice has been associated withobesity, hyperphagia and increased metabolic efficiency. In human, PCSK1 deficiency is amonogenic form of obesity. The first case of complete PCSK1 deficiency has been identifiedin 1997 and since two other cases were discovered. Deleterious PCSK1 mutations carrierswere either homozygous or compound heterozygous and presented severe phenotypes, such asobesity, intestinal troubles and endocrine disorders. Surprisingly, the family members whowere heterozygous for these mutations appeared clinically unaffected. Overall of these studieshighlighted PCSK1 as a candidate gene for obesity.We have therefore decided to assess the contribution of PCSK1 gene to polygenicobesity risk. To assess the contribution of PCSK1 to polygenic obesity risk, we genotyped tagsingle nucleotide polymorphisms in a total of 13,659 European individuals from eightindependent case-control or family-based cohorts. The non-synonymous variants rs6232,encoding N221D, and cluster rs6234-rs6235, encoding the Q665E-S690T pair, wereconsistently associated with obesity in adults and children (P=7.27 x 10-8 and P=2.31 x 10-12,respectively). Functional analysis revealed a significant impairment of the N221D mutant onPC1/3 protein catalytic activity.In continuity of this study we decided to assess the involvement of PCSK1 gene inmonogenic obesity, knowing that only three cases of complete PCSK1 deficiency have beenreported up to now. The objectives of this study were to evaluate the prevalence of rarePCSK1 mutations contributing to human obesity and to investigate the mode of inheritance ofobesity in the context of PCSK1 deficiency. We sequenced exons of the PCSK1 gene in 845non-consanguineous extremely obese subjects of European origin and we identified eightnovel PCSK1 non-synonymous mutations in eight carriers, all heterozygous. Wecharacterized the functional consequences of the detected mutations on PC1/3 protein and wefound that 62.5% of mutations detected were predicted to be deleterious in silico and werevealed that 87.5% of mutations had an effect on the autoactivation or on the enzymaticactivity of PC1/3 in vitro. In order to estimate the degree of penetrance for the sevenpathogenic mutations, we genotyped 6,060 obese and 6,274 lean subjects. We assessed a 6-fold enrichment of these PCSK1 mutations in obese subjects (P = 0.007). We provided thefirst evidence of an increased obesity risk in heterozygous carriers of loss of functionmutations in PCSK1 gene, confirming a co-dominant mode of transmission of obesity withincomplete penetrance for this gene. The penetrance of obesity was estimated to 54.5% for108heterozygous carriers of deleterious PCSK1 mutations. Partial PCSK1 deficiency mightexplain ~ 0.83% of extreme obesity.To conclude, in addition of the syndromic forms of obesity due to a complete PCSK1deficiency, we provided the strong evidence of the contribution of common non-synonymousvariants in obesity risk and we highlighted that a partial PCSK1 deficiency is associated withan increased risk of obesity.

The purpose of the present study is to compare a "traditional" behavioral therapy approach (based on selfcontrol techniques) with a previously unresearched "contextual therapy" for the treatment of overweight. The remainder of this chapter is devoted to a discussion of a variety of relevant behavioral techniques, an evaluation of them, and a discussion of a contextual model for the treatment of overweight.

Background and Purpose: More than one-third of American adults are obese. The prevalence of extreme obesity is rapidly rising. Nine medications are currently approved for weight loss yet they remain under utilized with the focus primarily on lifestyle modifications. The study's objective was to determine current prescribing patterns and attitudes of weight loss medications in the management of obesity among primary care providers (PCPs). Methods: PCPs were surveyed to determine practice patterns, attitudes, barriers, and facilitators for prescribing weight loss medications. Conclusions: A total of 105 surveys were completed. 76% of all PCPs did not prescribe weight loss medications for long-term weight loss therapy and 58% of PCPs had negative perceptions of pharmacotherapy as a treatment. Significant differences existed between prescribing patterns and attitudes of advanced practice clinicians and physicians. Safety concerns were identified as the greatest barrier. Having 2+ comorbidities and severe obesity were identified as facilitators for prescribing weight loss medications. Under utilization of pharmacotherapy suggests that PCPs may not have sufficient knowledge about medication safety profiles and efficacy. Delaying treatment until patients have reached a high level of morbidity may be less efficacious than earlier treatment. Implications for Practice: Education regarding effectiveness and risks of weight loss medications for obesity management is needed and earlier interventions with pharmacotherapy may prevent significant morbidity and mortality.

OBJECTIVE: High prepregnancy maternal body mass index (BMI) is associated with an increased risk in childhood overweight and obesity. This study sought to expand upon the research of this phenomenon/trend by examining the role of placental weight in inter-generational obesity risk. METHODS: This prospective birth cohort study was conducted at Boston Medical Center in Boston, Massachusetts. Between 1998 and 2016, the study recruited and tracked 1,025 mother-infant pairs who have been followed from birth prospectively up to age 19 and who had data on placental pathology along with pre-, peri-, and post-natal variables, including maternal and child BMI. This study analyzed 6 Groups defined by placental weight tertiles and maternal overweight and obesity (BMI ≥ 25 kg/m2) (binary). Group 0 includes lowest placental tertile and maternal not overweight and obesity. Group 1 includes lowest placental tertile and maternal overweight and obesity. Group 2 includes middle placental tertile and maternal not overweight. Group 3 includes middle placental tertile and maternal overweight and obesity. Group 4 includes highest placental tertile and maternal not overweight. Group 5 includes highest placental tertile and maternal overweight and obesity. MAIN OUTCOMES AND MEASURES: Child BMI z-score was calculated according to United States reference data for specific age and sex. Childhood overweight and obesity was defined as an BMI in the 85th percentile or greater for age and sex. Maternal overweight and obesity was defined as a BMI of 25kg/m2 or greater, and placental weight was classified into tertiles based on sex- and gestational age. RESULTS: The mean (SD) maternal age at delivery was 28.7 (6.6) years and the mean (SD) child age at last visit was 9.5 (4.9) years. Among 1,025 mothers, 54.15% were overweight with an average BMI of 27.0 kg/m2. 68.98% of mothers were black, 76.5% never smoked, and 62.73% had less than a high school education. Among 1,025 children 447 (43.61%) were overweight. As expected, maternal overweight and obesity was associated with the highest risk for childhood overweight and obesity, with an odds ratio of 3.752 (95% CI, 2.137-6.588) as well as the largest increase in child BMI z-score. The strong association remained after adjusting for placental weight and other covariables, including birth weight. When maternal overweight and obesity and placental weight were analyzed in combined groups (0-5), they jointly increased the risk of child overweight or obesity. Using group 0 as reference, the group 5 had the highest risk of child overweight or obese and the largest increase in child BMI z-score. CONCLUSIONS: In this urban low-income prospective birth cohort, we observed a strong inter-generational link of overweight or obesity. Furthermore, there was an additive effect of maternal overweight and obesity and placental weight on child risk of overweight and obesity. Additional studies are warranted to replicate our findings and further investigate the biological pathways underlying the inter-generational obesity risk. / 2021-06-17T00:00:00Z

Liu Kin Hung. / "May, 2003." / Thesis (Ph.D.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (p. 153-193). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Mode of access: World Wide Web. / Abstracts in English and Chinese.

Relatively few studies have examined the effects of psychostimulants in obese subjects. Using the dietary obese rat model, the present experiments determined the reductions in food intake (hypophagia) and increases in locomotion (hyperlocomotion) induced by cocaine in diet-induced obese prone (DIO-prone) rats and diet resistant prone (DR-prone) rats as well as diet-induced obese (DIO) rats and diet resistant (DR) rats. In Experiment 1, thirty-six male Sprague-Dawley rats were given intra-peritoneal (i.p.) injections of cocaine (0, 10, 20, and 30 mg/kg) immediately prior to placement into locomotor chambers outfitted with a food source and a water source for a 60-minute test period. In Experiment 2, the same rats were exposed to a high-fat diet, and were subsequently divided into groups according to the extent of the weight gain (high weight gainers œ DIO group, low weight gainers œ DR group, and residual weight gainers œ MIX group). The rats were retested for reactivity to cocaine using conditions similar to those in Experiment 1. Rats injected with cocaine prior to high-fat exposure (Experiment 1) showed a dose dependent suppression of food intake, as well as a dose dependent increase in locomotor activity, with DR-prone rats exhibiting an enhanced degree of cocaine-induced hypophagia, as well as cocaine-induced hyperlocomotion as compared to the other groups. In Experiment 2, DIO rats exhibited a suppression of food intake after injection of 10 mg/kg cocaine, as well as an increase in locomotor activity that was significantly greater than noted in the other groups. When the results of Experiment 1 were analyzed as a function of prospective body weight gain (as opposed to placement into distinct groups), reactivity to cocaine decreased as body weight gain increased. In contrast, after high-fat exposure and weight gain, increased body weight gain was associated with an increased magnitude of suppression in food intake after cocaine administration. Similar patterns of differential cocaine sensitivity were observed for cocaine hyperlocomotion in Experiment 2. These studies indicate that although the propensity to develop obesity is associated with a diminished cocaine response, cocaine reactivity is enhanced after the induction of obesity.