Influences Of Socioeconomic Status, Dietary Factors And Physical Activity On Overweight And Obesity Of Australian Children And Adolescents

摘要

The increasing prevalence of overweight and obesity in young people is a major global public health concern, especially in developed countries. In Australia, studies in 2001 have suggested that 20% of boys and 21.5% of girls aged 7-15 years were overweight or obese, while in 1985 the figures were 10.7% and 11.8%, respectively. In the short-term, overweight and obese children and adolescents suffer from both adverse physical and psychological consequences. The most significant long-term consequence of childhood obesity is its persistence into adulthood, along with numerous associated health risks. A number of studies have shown that there is an association between being an overweight child and subsequent adulthood obesity. In general, childhood overweight and obesity is a multifactorial disease and its development is due to multiple interactions between genes and environment. A number of risk factors such as socioeconomic status, dietary patterns, and physical activity have been frequently identified as contributors to its development. However, the results of recent studies provide conflicting evidence. The statistical limitations also make it difficult to compare the studies on childhood obesity between countries. In addition, existing research in Australia that examines the contribution of different risk factors to childhood obesity is limited. There are no published data on the relationship between overweight/obesity, dietary patterns, and physical activity/inactivity in Australian children and adolescents. This study examined the influences of household income, dietary factors, physical activity/inactivity and ethnicity on overweight and obesity among Australian children and adolescents. It also explored the relationship between self-reported weight and height to actual weight and height in older Australian adolescents in order to clarify the accuracy of self-reported data among Australian youth.Data from the two national cross-sectional surveys, the 1995 Australian National Health Survey (NHS) and the 1995 National Nutrition Survey (NNS) were analysed to explore the influences of household income, intake of energy and fat and percentage of energy from fat on childhood obesity. The study focused on 1585 children and adolescents aged 7-15 years. These data were also used to examine the relationship of self-reported weight and height to measured weight and height in older adolescents. Additionally, another cross-sectional survey among a group of Australian primary school children from a multi-cultural school in southern Brisbane was undertaken as well as providing indicative data on the relationship of overweight/obesity to physical activity levels and ethnicity, and to provide a protocol on the methodology and practicality of measuring physical activity level in such a school setting.The results suggested that boys from households with low incomes were more likely to be overweight or obese compared with those from households with higher incomes. Having parents, especially mothers, who were overweight or obese increased the risk of children being overweight or obese. The results do not provide evidence that there are statistically significantly differences in the average intake of energy and fat and percentage of energy from fat between non-overweight and overweight or obese boys and girls. The correct classification of weight or obesity from self-reported height and weight by Australian older adolescents was about 70%, bias in reporting weight and height is higher among overweight or obese older adolescents than non-overweight counterparts. In addition, preliminary, indicative data from the pilot study on the relationship between body mass index (BMI) and physical activity in 10-12 year old Australian school children from a multi-cultural school revealed that the average daily physical activity level (PAL) was 2.3 Metabolic Equivalents (METs) when the PAL was measured using self-reported activity diary. The proportion of light, moderate and heavy PAL was 2.9%, 20.4% and 76.7% in children, respectively. Additionally no ethnic differences in the prevalence of overweight /obesity was found. There was no statistically significant difference in average daily TV view times between non-overweight and overweight or obese boys and girls. The average daily number of steps measured using pedometer in the weekdays was 16,505 in boys and 12766 in girls. Most of boys (94.0%) have a medium and over level of steps taken daily while nearly one-third of the girls had not reached the minimum level in the number of steps for optimal health. However it must be noted this school-based study was a small cross-sectional survey in a single school. The results should be viewed as indicative, not generalisable. The study does not provide any longitudinal data on physical activity patterns and the trends in relationship to body mass index. In spite of the limitations of this study, it did provide some preliminary data on PAL and its relationship to overweight/ obesity among young Australian schoolchildren from diverse cultural backgrounds. Most importantly, this pilot study has provided a protocol on the methodology and practicality of measuring physical activity levels of children using self-reported activity diaries and pedometers in a multicultural school setting. A number of strategies for the prevention and treatment of childhood overweight and obesity are discussed. In future studies, a population-based and randomly selected sample would ensure findings that are more representative of general Australian children, and the longitudinal studies would help to define the association between the risk factors and childhood obesity, as well as enabling conclusions on causality to be drawn.