published_or_final_version / Community Medicine / Master / Master of Public Health

Background: With adolescent obesity increasing in many developed and developing countries, many studies have investigated the effects of dietary habits on adolescent obesity. However, night-eating, which may lead to extra caloric intake and weight gain, is understudied. Given adolescents’ behavior patterns required during this period to be likely to influence long term behaviors, the present study investigated the prevalence of night-eating in Hong Kong adolescents and its association with weight status, dinner habits, bedtime, and the interval between dinner time and bedtime. Methods: This study was a secondary analysis with a sample of 24885 adolescents based on the dataset of Hong Kong Student Surveillance (HKSOS) project which was a school-based cross-sectional survey conducted in 2006/07. The subjects reported the number of days they had night-eating per week, the usual time they had dinner, the time spent on dinner, and bedtime. The interval between dinner time and bedtime was calculated and classified as long (4 hours or more) or short (below 4 hours). Weight status was estimated based on the self-reported weight and height. The prevalence of night-eating and distributions of dinner habits and bedtime were examined using descriptive statistics (mean, standard deviation and percentage). Logistic regression and multiple linear regression models with robust standard errors accounting for school clustering effects were used (Stata 11.0) to estimate crude and adjusted odds ratios (OR) and regression coefficients for associations about night-eating. Results: Half (50.2%) the subjects reported any night-eating and 21.9% reported frequent night-eating of more than three days a week. The change of BMI z-score was positive associated with night-eating (Coefficient: 0.204; 95%CI: 0.175-0.233), and night-eaters were 13% (95%CI: 6%-20%) more likely to be obese. Compared with early dinner time group, the normal dinner time group was 11% (95% CI: 6%-15%) less likely to have night-eating. Students who reported normal and slow eating speed were 30% (95 % CI: 22%-39%) and 147% (95% CI: 113%-187%) more likely to have night-eating compared with quick eating speed group; the late-sleepers were 43% (95% CI: 35%--53%) and 25% (95%CI: 18%--34%) more likely to have night-eating on weekday and weekend, respectively, compared with early-sleepers. Besides, it was observed that adolescents having longer interval between dinner time and bedtime were 22% (95% CI: 5%--42%) more likely to have night-eating. Conclusion: The prevalence of night-eating was 50.2% in Hong Kong students. The night-eating was positively related with obesity, and the relationship was the first time to be estimated in Hong Kong adolescents. Besides, the relative early dinner time (compared with bedtime), slow dinner speed, late bedtime and long interval between dinner time and bedtime were positively associated with night-eating. / published_or_final_version / Public Health / Master / Master of Public Health

Background: As modern nations undergo demographical and epidemiological transitions, infectious diseases are replaced by non-communicable and chronic illnesses as the main source of ill-health. In particular, the obesity epidemic is of important public health concern as the prevalence of overweight and obesity continues to increase at an alarming rate globally. The trend in childhood and adolescent obesity is also escalating rapidly as people are gaining excess weight at younger ages, representing a growing threat as obesity is linked to a myriad of detrimental psychosocial and physical health consequences which may persist through adulthood. The fundamental cause of obesity is energy imbalance with energy intake exceeding energy expenditure within the human body. Total daily energy expenditures can vary substantially among individuals due to non-exercise activity thermogenesis (NEAT), which accounts for the energy expended from activities we do in daily living, including spontaneous behaviours such as fidgeting. Cumulatively, trivial activities such as fidgeting may accrue to have a significant impact on total daily energy expenditure. Studies have shown that NEAT levels increase or decrease in response to over- and under-feeding, respectively, to counterbalance changes in energy homeostasis. Therefore, fidgeting and NEAT may be an important component in maintaining weight. Decreased levels of fidgeting and NEAT has been hypothesized to be more common among obese individuals as the body fails to activate NEAT in response to over-eating, leading to weight gain. Understanding the correlates of fidgeting and non-exercise physical activity will be helpful in supplementing the design and implementation of effective strategies against obesity. Objective: To investigate the correlates of fidgeting among Hong Kong adolescents, including the association between fidgeting and weight status. Methods: Post hoc statistical analysis was conducted using secondary data from the Hong Kong Student Obesity Surveillance (HKSOS) Project from 2006-2007, which surveyed 34 678 students across 42 secondary schools in Hong Kong. Multivariate logistic regression analyses yielded crude and adjusted odds ratios for the associations of background characteristics, lifestyle characteristics, and dietary intake on fidgeting. Multinomial logistic regression analyses estimated crude and adjusted odds ratios to evaluate the associations between weight status and fidgeting/non-exercise physical activity. Results: Among the sample of Hong Kong adolescents, subjects who were male, older, born outside of Hong Kong, and had daily consumption of fresh fruits, fresh vegetables, and protein were associated with having lower odds of fidgeting. In contrast, high paternal control, high maternal control, smoking, alcohol consumption, elevated levels of daily screen time, exercise time, non-exercise physical activity time, and increased intake in deep fried/fatty foods, snacks/fizzy drinks, coffee, and tea were all associated with having higher odds of fidgeting. Fidgeting did not appear to have any significant relationships with weight status. However, non-exercise physical activity was associated with increased odds of being both underweight and overweight. Conclusions: The results from this study indicate that there are meaningful associations between fidgeting and various correlates, including background demographic characteristics and modifiable behavioural factors. Further studies are required to gain a better understanding of the correlates of fidgeting and their implications to public health. / published_or_final_version / Public Health / Master / Master of Public Health

Interdiction：Little attention has been paid on the association between weight status and Hong Kong adolescents’ sexuality. Nowadays, increasing incidence of risky sexual behaviours caused negative outcomes among adolescents. Studies showed that obesity population suffer difficult social relationships and had bad school performance. The aim of this study is to identify associations between BMI, BSD status and sex-related knowledge, attitudes and behaviours among Hong Kong adolescents. Methods: This population-based study uses secondary data from Youth Sexuality Study (YSS), it is a self-administered questionnaire conducted by Hong Kong Family Planning Association (HKFPA). 2329 secondary school Form 3 to Form 7 students successfully completed the survey were included in the study. The primary outcome is sexual knowledge scores, sexual attitudes scores, dating status and intercourse status. Body mass index (BMI) was estimated to classify weight status categories (categorized by normal weight, underweight, overweight, and obese) according to IOTF cutoffs and WHO BMI guideline. Body shape dissatisfaction was defined as a discrepancy between current and ideal body shape based on a figure rating scale. Age, gender, grade, parental education levels and BMI were adjusted as confounders. Generalized linear models were used to analyze the association between weight status and sex-related knowledge, and attitudes. A binary logistic regression was used to compare associations between weight status and sex-related behaviours and provide odds ratios (OR). Results: 7.1% of respondents were classified into underweight, 83.4% normal weight, 6.3% overweight and 3.2% obese. Obese students had an average a sexual attitudes score 1.26 (95% CI: 1.21, 6.96) point higher than that of the normal weight students, and obese girls had a mean attitudes score 1.24 higher than normal weight girls, it is significant association. A means of 0.59 points higher of sexual attitudes score for desired a larger BS students compared to no dissatisfaction. Odds ratio was showed for overweight boys of 1.74 (95% CI: 1.08, 2.79) showed likely to had dating. There was no significant association of knowledge score with current weight status after adjustment of confounders. Likewise, there was no significant association between weight status and intercourse status. Conclusion: Overweight and desired a smaller body shape was significantly associated with sexual attitudes that are accepting of risk-taking behaviours. Being overweight and desiring a smaller body shape was also associated with increased probability of ever having dated, but only in males. This study provided some findings to suggest adolescents’ sexuality and weight status for Hong Kong government’s policy making agenda. There need to be more allocation of education resources in expanding mental and social-relationship consultancy for obesity adolescents and those who desired a smaller body shape, and to develop risky sex-related behaviours prevention to obesity male adolescents. / published_or_final_version / Public Health / Master / Master of Public Health

published_or_final_version / Zoology / Master / Master of Philosophy

published_or_final_version / Community Medicine / Doctoral / Doctor of Philosophy

Xie, Yaojie. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references (leaves 171-185). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese; appendix in Chinese.