Thesis (M. P. H.)--University of Hong Kong, 2005. / Also available in print.

Thesis (M.P.H.)--University of Hong Kong, 2005.

INTRODUCTION Professional jockeys are considered elite sportsmen competing in a sport with certain weight restrictions. Horse racing is categorized as a “weight-making” sport where jockeys can benefit from attaining and/or maintaining a specific weight for competition. The minimum riding weight for professional jockeys and apprentice jockeys who are race riding is currently 52 kg. The lighter the jockey (i.e. the closer he can remain to the minimum weight of 52 kg) the more rides may be allocated to him (and the more money he will earn). This places a great deal of pressure on the jockey to maintain a low body weight, in order to attain rides. Unlike other weight category sports, horse riding does not have an “off season”, therefore jockeys are constantly pressured to maintain a minimal weight. Consequently this may result in unhealthy eating habits, dangerous weight control practices and compromised health. Research on the weight making practices of apprentice jockeys is scarce. In fact, there is currently no published data available on the South African apprentice jockey. The aim of this study was therefore to examine the dietary intake, energy availability and weight control practices of male apprentice jockeys residing at the South African Jockey Academy. METHODS Twenty one male flat jockey apprentices of different race groups, between the ages of 16 and 20 years were recruited to take part in this cross sectional observational study. Height, weight and body composition (body fat percentage and fat free mass) were measured. The apprentices completed a 59-item nutrition, health and lifestyle questionnaire including questions on weight control and weight making practices. Dietary intake was recorded with a 24-hour dietary recall on four non-consecutive days including a rest day, two training days, and a race day. On these days, exercise energy expenditure was also recorded with Actiheart© monitors with the aim to calculate energy availability. MAIN FINDINGS Total mean reported energy intake of the participants was 7088±2337kJ (35.5±12.5kcal/kg fat free mass [FFM]) and below the recommendations for athletes exercising several hours per day for most days of the week. The micronutrient intakes of the majority of these jockeys were also low (i.e. <67% of recommended intake). Mean calculated energy availability (EA) over two training days and one rest day was 27.1±16.7 kcal/kg FFM and regarded as low (i.e.<30kcal/kg/FFM). Furthermore, the majority of apprentices (88%) had a low EA on the training days. Ninety one percent of the jockeys reported the use of one or more weight control method including food avoidance (81%), restricting food intake and skipping meals (67%), exercising to sweat (48%) and using the sauna (43%). The top three reported side effects from making weight included thirst (80%), hunger (75%) and tiredness (75%). CONCLUSION In conclusion, the results of the present study showed that the majority of South African apprentice jockeys are practicing weight control methods, specifically restricting energy and food intake, to control their weight. This was supported by the mean low dietary energy intake and sub-optimal mean energy availability. These apprentice jockeys are therefore at risk for long-term health consequences including low bone mineral density. / MSc (Nutrition), North-West University, Potchefstroom Campus, 2015

INTRODUCTION Professional jockeys are considered elite sportsmen competing in a sport with certain weight restrictions. Horse racing is categorized as a “weight-making” sport where jockeys can benefit from attaining and/or maintaining a specific weight for competition. The minimum riding weight for professional jockeys and apprentice jockeys who are race riding is currently 52 kg. The lighter the jockey (i.e. the closer he can remain to the minimum weight of 52 kg) the more rides may be allocated to him (and the more money he will earn). This places a great deal of pressure on the jockey to maintain a low body weight, in order to attain rides. Unlike other weight category sports, horse riding does not have an “off season”, therefore jockeys are constantly pressured to maintain a minimal weight. Consequently this may result in unhealthy eating habits, dangerous weight control practices and compromised health. Research on the weight making practices of apprentice jockeys is scarce. In fact, there is currently no published data available on the South African apprentice jockey. The aim of this study was therefore to examine the dietary intake, energy availability and weight control practices of male apprentice jockeys residing at the South African Jockey Academy. METHODS Twenty one male flat jockey apprentices of different race groups, between the ages of 16 and 20 years were recruited to take part in this cross sectional observational study. Height, weight and body composition (body fat percentage and fat free mass) were measured. The apprentices completed a 59-item nutrition, health and lifestyle questionnaire including questions on weight control and weight making practices. Dietary intake was recorded with a 24-hour dietary recall on four non-consecutive days including a rest day, two training days, and a race day. On these days, exercise energy expenditure was also recorded with Actiheart© monitors with the aim to calculate energy availability. MAIN FINDINGS Total mean reported energy intake of the participants was 7088±2337kJ (35.5±12.5kcal/kg fat free mass [FFM]) and below the recommendations for athletes exercising several hours per day for most days of the week. The micronutrient intakes of the majority of these jockeys were also low (i.e. <67% of recommended intake). Mean calculated energy availability (EA) over two training days and one rest day was 27.1±16.7 kcal/kg FFM and regarded as low (i.e.<30kcal/kg/FFM). Furthermore, the majority of apprentices (88%) had a low EA on the training days. Ninety one percent of the jockeys reported the use of one or more weight control method including food avoidance (81%), restricting food intake and skipping meals (67%), exercising to sweat (48%) and using the sauna (43%). The top three reported side effects from making weight included thirst (80%), hunger (75%) and tiredness (75%). CONCLUSION In conclusion, the results of the present study showed that the majority of South African apprentice jockeys are practicing weight control methods, specifically restricting energy and food intake, to control their weight. This was supported by the mean low dietary energy intake and sub-optimal mean energy availability. These apprentice jockeys are therefore at risk for long-term health consequences including low bone mineral density. / MSc (Nutrition), North-West University, Potchefstroom Campus, 2015

It is a vitally important task to achieve control of the weight and center of gravity of lightship during building a new ship. If the lightship weight is slightly out of control, the deadweight inadequacy and a deviation from the initial design target will be caused. The basic performance and function of a ship at sea are also resulted. Furthermore, if the lightship weight is incompletely under control, it will bring about an unsafe vessel, ship-delivery difficulty and a severe loss for shipbuilder. Docking arrangement is optimized to allocate by using the state-of-the-art finite element method to analyze the lightweight distribution as the load and the ship girder as a beam; in addition, the dock is recognized as a spring-liked elastic foundation subjected to compression only. It is verified by comparison between measurement of the lightship weight by means of the weight control system on land and the traditional inclining experiment. Based on the results, it can be shown that the whole system is reliable, available and efficient. The load cell is utilized as a component of the weight control system to measure the compressive force (i.e., ship weight) at a specified dock. The main function of the system is to determine the lightweight and its C.G. on-land construction instead of the time-consuming and labor-wasting traditional way. The presented methodology will be beneficial for weight control of a new-ship building in the future.

A utilização de técnicas comportamentais associadas a orientação de dieta com restrição calórica e a modificação das cognições, crenças e atitudes sobre alimentação e controle de peso podem ser uma modalidade de intervenção que promove melhores resultados ao longo do tempo. Objetivo: Avaliar as cognições e atitudes de mulheres obesas relativas à alimentação e controle de peso e as alterações ocorridas após a participação em programa de emagrecimento. Metodologia: foram acompanhadas 41 mulheres com excesso de peso. Estas foram alocadas para análise em 3 núcleos: núcleo 1) mulheres participantes de programa de emagrecimento; núcleo 2) lista de espera; e núcleo 3) mulheres desistentes. As mulheres do núcleo 1 foram entrevistadas antes e após a intervenção e o material da entrevista foi utilizado para produzir o Discurso do Sujeito Coletivo. O programa de emagrecimento teve as seguintes características: 12 sessões; sessões uma vez por semana; atividades em grupo. Resultados: as mulheres do núcleo 1 apresentaram maior redução de peso (Média: -4,64kg; -5,51%) dos que as mulheres participantes do núcleo 2 (Média: -0,16kg; -0,31%) e do núcleo 3 (Média: -0,50 kg; -051%) esta diferença foi estatisticamente significante (p 0,000). A análise do Discurso do Sujeito Coletivo mostrou modificação das crenças quanto às características que dietas para perda de peso devem apresentar e pensamentos relativos a forma como o controle da ingestão de alimentos deve ocorrer. Conclusão: estes achados apontam para a necessidade de buscar modalidades de intervenção que provoquem modificações cognitivas e atitudinais para que o controle de peso se efetue de maneira permanente para as mulheres. / Behavioral based interventions associated with moderate caloric restriction and diet and weight control beliefs modification may be an effective form of weight control in the long term. Objective: Evaluate cognitions and attittudes related to eating habits and weight control among overweight and obese women enrolled in a weight control program. Methodology: the program was a group intervention, 12 sessions weekly designed. Forty one overweight women were allocated in 3 groups: 1) behavioral based and diet beliefs modification program; 2) waiting list; 3) drop-outs from category one. Initial and Final interviews with women allocated in the category 1 were done and were used in a qualitative analysis. Results: Women allocated in group 1 lost significantly (p 0,000) more weight (-4,64kg; -5,51%) than women in group 2 (-0,16kg; -o,31%) and group 3 (-0,50 kg; -051%). The qualitative analysis demonstrated changes in diet and weight loss related thoughts and beliefs. The narrative showed improvement in thoughts about energy dense food and the composition of an ideal weight loss diet. At the final interview women described a more self-conscious eating style. Conclusions: Weight Control Programs should address the improvement of food and weight related cognitions and attitudes in order to promote permanent weight control among overweight women.

A utilização de técnicas comportamentais associadas a orientação de dieta com restrição calórica e a modificação das cognições, crenças e atitudes sobre alimentação e controle de peso podem ser uma modalidade de intervenção que promove melhores resultados ao longo do tempo. Objetivo: Avaliar as cognições e atitudes de mulheres obesas relativas à alimentação e controle de peso e as alterações ocorridas após a participação em programa de emagrecimento. Metodologia: foram acompanhadas 41 mulheres com excesso de peso. Estas foram alocadas para análise em 3 núcleos: núcleo 1) mulheres participantes de programa de emagrecimento; núcleo 2) lista de espera; e núcleo 3) mulheres desistentes. As mulheres do núcleo 1 foram entrevistadas antes e após a intervenção e o material da entrevista foi utilizado para produzir o Discurso do Sujeito Coletivo. O programa de emagrecimento teve as seguintes características: 12 sessões; sessões uma vez por semana; atividades em grupo. Resultados: as mulheres do núcleo 1 apresentaram maior redução de peso (Média: -4,64kg; -5,51%) dos que as mulheres participantes do núcleo 2 (Média: -0,16kg; -0,31%) e do núcleo 3 (Média: -0,50 kg; -051%) esta diferença foi estatisticamente significante (p 0,000). A análise do Discurso do Sujeito Coletivo mostrou modificação das crenças quanto às características que dietas para perda de peso devem apresentar e pensamentos relativos a forma como o controle da ingestão de alimentos deve ocorrer. Conclusão: estes achados apontam para a necessidade de buscar modalidades de intervenção que provoquem modificações cognitivas e atitudinais para que o controle de peso se efetue de maneira permanente para as mulheres. / Behavioral based interventions associated with moderate caloric restriction and diet and weight control beliefs modification may be an effective form of weight control in the long term. Objective: Evaluate cognitions and attittudes related to eating habits and weight control among overweight and obese women enrolled in a weight control program. Methodology: the program was a group intervention, 12 sessions weekly designed. Forty one overweight women were allocated in 3 groups: 1) behavioral based and diet beliefs modification program; 2) waiting list; 3) drop-outs from category one. Initial and Final interviews with women allocated in the category 1 were done and were used in a qualitative analysis. Results: Women allocated in group 1 lost significantly (p 0,000) more weight (-4,64kg; -5,51%) than women in group 2 (-0,16kg; -o,31%) and group 3 (-0,50 kg; -051%). The qualitative analysis demonstrated changes in diet and weight loss related thoughts and beliefs. The narrative showed improvement in thoughts about energy dense food and the composition of an ideal weight loss diet. At the final interview women described a more self-conscious eating style. Conclusions: Weight Control Programs should address the improvement of food and weight related cognitions and attitudes in order to promote permanent weight control among overweight women.

The main goal of this study is to examine the relationship between weight control expectancies, weight concerns, smoking rate and perceived likelihood of smoking in the future among Spanish adolescents. Specifically, I intend to explore the potential moderator role of weight concerns on the relationship between weight control expectancies and smoking rate, as well as between weight concern and perceived likelihood of smoking in the future. Additionally, I want to investigate the possible meditational role of weight control expectancies on the relationship between weight concerns and smoking rate and likelihood of smoking in the future, respectively. The participants were 311 Spanish adolescents (M = 15.20; SD = 1.63; 174 female and 137 male) from schools in Alicante, Spain. The students completed questionnaires regarding smoking history and status. They also responded to questions regarding smoking expectancies and weigh concerns. Results suggested differences between smokers and nonsmokers in weight control expectancies and fear of fatness regardless of gender. The moderator model of weight concerns was not supported by findings. The results prove the meditational role of weight control expectancies on the relationship between fear of fatness and smoking rate, as well as between fear of fatness and perceived likelihood of smoking in the future. Implications, directions for future research and limitations of the study are discussed.

published_or_final_version / abstract / toc / Clinical Psychology / Master / Master of Social Sciences

Hyaluronic acid (HA) is a high value biopolymer that has numerous biomedical and cosmetic applications. It is currently derived from two sources, namely animal tissues and bacterial fermentation (Fong Chong et al. 2005). The molecular weight (Mw) of HA can vary from several hundred thousand dalton (Da) to approximately 8 MDa (Widner et al. 2005). High Mw HA has surgical applications, and therefore constitutes a major component of the lucrative HA market. The current need is largely met by extraction from animal tissues, e.g., rooster comb and bovine vitreous humor (Shiedlin et al. 2004). However, the potential of contamination with adventitious agents (e.g., viruses) have raised regulatory concerns regarding the use of animal extracts in pharmaceutical products. Moreover, with recent reports of zoonotic diseases (e.g., bovine spongiform encephalitis and avian influenza virus), pharmaceutical companies are moving towards microbial HA sources. Although HA obtained from bacterial fermentation does not have the problem of viral contamination, this approach has not yet resulted in a process where HA of sufficiently high Mw for surgical applications can be derived. While attempts have been made to produce higher Mw HA through cross-linking, cross-linked HA is undesirable for certain medical procedures (e.g., ophthalmic applications) which requires a natural polymer with a short half-life. Nevertheless, due to its availability and the relative ease of purification, bacterial fermentation has the potential of replacing extraction from animal tissues as a preferred commercial source of HA. This thesis presents a good example of a metabolic engineering study where modern techniques (e.g., molecular biology, fermentation and omics technologies) are used to explain complex cell metabolism. The hypothesis for this study was that the precursors to HA, i.e., UDP-glucuronic acid and UDP-N-acetylglucosamine and consequently the genes involved in precursor generation, are important for HA Mw. However, environmental manipulation, e.g., anaerobic versus aerobic or glucose versus maltose, often results in large global changes in metabolite concentration and enzyme activities. This makes it impossible to resolve issues related to Mw control. Classical statistical methods do not provide a meaningful inference as the number of explanatory variables always exceeds the number of independent observations. Hence, it is difficult to distinguish between causative and accidental correlation. This work first examined the influence of manipulation of metabolite concentrations in the hyaluronan pathway to find an explanation for the mechanism of Mw control. To achieve this, the five essential genes of the hyaluronan synthesis (has) operon in Streptococcus equi subsp. zooepidemicus (S. zooepidemicus) were first examined. These genes are involved in two pathways which lead to the production of either UDP-glucuronic acid or UDP-N-acetylglucosamine. Overexpression of genes involved in UDP-glucuronic acid biosynthesis decreased HA Mw, while overexpression of genes involved in UDP-N-acetylglucosamine biosynthesis increased HA Mw. The Mw variation generated provided a stepping stone for further understanding of Mw control of HA. The highest Mw observed was achieved with combined overexpression of pgi and glmU. This study proved that there is a positive correlation between UDP-N-acetylglucosamine and Mw. The first model for HA Mw control based on the concentration of activated sugar precursors is described in this study (Chapter 3). This correlation observed led to the hypothesis that high Mw HA can be achieved when an appropriate balance of the two HA precursor is maintained. Three genes in the two precursor pathways are not found in the has operon of S. zooepidemicus. To obtain a complete overview of all genes in the HA pathway, these genes were also examined using overexpression studies. Individual overexpression of these genes had negligible effects on HA Mw and production. Despite the positive correlation previously observed between UDP-N-acetylglucosamine and Mw, sequential overexpression of genes involved in the UDP-N-acetylglucosamine precursor pathway did not increase Mw of HA produced. This is surprising since the highest pool of UDP-N-acetylglucosamine was achieved in this case. This suggests that a threshold effect is present in the correlation between UDP-N-acetylglucosamine and Mw. This threshold effect may be defined by a balance between the two precursors. To investigate this phenomenon further, the precursor ratio was also manipulated by co-metabolising glucose and N-acetylglucosamine. Similar to the previous experiment, a significant increase in UDP-N-acetylglucosamine levels was observed despite only a marginal increase in Mw (Chapter 4). Surprisingly, an increase in Mw was observed with the introduction of a plasmid in S. zooepidemicus. This plasmid effect was studied on a global scale using transcriptome and proteome analysis to understand the changes occurring in the system. The increase in Mw due to the plasmid effect is independent of the functions, i.e., nisin promoter or antibiotic resistance, encoded in the plasmid. A gene involved in UDP-N-acetylglucosamine production, UDP-N-acetylglucosamide 1-carboxivinyltransferase (murA), was significantly down-regulated in both the plasmid bearing strain and the high Mw strain (pgi). In addition, overexpression of murA decreased both the concentration of activated sugar precursors and HA Mw. There was however no evidence of down-regulation of murA in the plasmid containing strain from transcriptomics data. This suggests that control is exerted either at the translation level or by protein degradation (Chapter 5). This thesis contributes and represents an ongoing effort to understand the elusive mechanism of Mw control of HA.