The high prevalence of overweight and obesity among older Australian adults and their strong association with an increased risk of ill health, functional limitation and disability, are well documented. This thesis examines the assessment and management of overweight and obesity in older adults. Meta-analyses of randomised controlled trials were undertaken to assess the effects of psychological interventions and of exercise on body weight and health. A series of analyses were then undertaken using data from the 1053 participants enrolled in The Tasmanian Older Adult Cohort Study, an ongoing prospective cohort study whose aim is to identify the environmental, genetic and biochemical factors associated with the development and progression of a number of chronic diseases. The purpose of the analyses was to investigate changes in body composition (measured using dual-energy X-ray absorptiometry) that occur with age, the most accurate field methods for assessing body composition in different age groups, the influence of lifestyle risk factors on body composition, and the complex interrelationships between age, lifestyle, body composition and cardiovascular disease risk factors. Results demonstrate that body fat increases and lean body mass decreases with increasing age in older adults. The most accurate field methods for assessing body composition in older adults are body mass index (BMI) and waist circumference. Lean body mass is predominantly influenced by age in older adults and decreases as age increases. Body fat, however, is predominantly influenced by lifestyle risk factors. Physical activity levels, smoking and alcohol consumption in females are associated with lower body fat, whereas the presence of chronic pain and alcohol consumption in males are associated with higher body fat. In younger and middle aged adults, meta-analyses of randomised controlled trials demonstrate that exercise is an effective weight loss intervention, particularly when combined with low fat or low calorie diets. Exercise also improves factors commonly associated with cardiovascular disease, even in the absence of weight loss. Meta-analyses of randomised controlled trials also demonstrate that adults who are overweight or obese can reduce weight with psychological interventions, particularly behavioural and cognitive behavioural interventions. In older adults, observational data demonstrate that higher levels of pedometer-determined physical activity are associated with lower body fat, supporting the efficacy of physical activity or an active lifestyle as a weight loss intervention in this group also. The greatest impact of physical activity on body fat is observed when participants increase activity levels to greater than 7 500 steps per day. However, higher levels of physical activity are not associated individually with improved blood pressure, lipids or fasting serum glucose. Instead, higher physical activity levels are associated with a lower total number of cardiovascular risk factors, suggesting that in older adults, physical activity reduces the likelihood of multiple cooccurring cardiovascular disease risk factors. The studies within this thesis provide an evidence base for the continued development of an understanding of the assessment and management of overweight and obesity in older adults. A number of research priorities have also been highlighted. These include the need for long-term randomised controlled clinical trials in older adults in order to: assess the efficacy and safety of multi-component weight loss therapies (diet, physical activity and psychological therapy); determine the combination of physical activity and dietary therapy that will maximize loss of body fat while maintaining lean body mass in older adults for whom weight loss therapy is appropriate; and assess the effect of weight loss, diet and physical activity on clinical outcomes, particularly chronic disease end-points and risk factors in older adults. Longitudinal studies are required to: explore the interrelations between ageing, physical activity levels, body composition and cardiovascular disease risk in older adults; determine the causal relationships that exist between lifestyle risk factors, body composition and chronic disease in older adults; and better assess the effect of alcohol consumption on body composition using sensitive measures in older adults.
| Identifer | oai:union.ndltd.org:ADTP/253228 |
| Creators | Shaw, Kelly Anne-Marie |
| Source Sets | Australiasian Digital Theses Program |
| Detected Language | English |
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