| Summary: | This thesis describes the behavioural compensatory responses and metabolic changes in response to a single exercise session and training programmes in overweight and obese women and consists of a literature review (Chapter 1), a general methods chapter (Chapter 2), three experimental chapters (Chapter 3- Chapter 5) and a general discussion and conclusions chapter (Chapter 6). Experimental chapter 3 presents a study which aimed to investigate the impact of a single moderate-intensity cycling exercise session with energy expenditure of approximately 2 MJ on appetite measures, energy intake and metabolic variables in response to four ad libitum meals in overweight and obese females. Twelve sedentary, overweight and obese women underwent one exercise and one control trial each over two consecutive days. Appetite and metabolic variables such as glucose, insulin and triglycerides were measured frequently and four buffet meals were served throughout each trial. The findings suggest that a single exercise session performed by overweight and obese women does not elicit compensatory responses in appetite and energy intake and reduces triglyceride concentration by 17% in response to an ad libitum breakfast consumed 14 hours after exercise. Chapter 4 aimed to examine the extent to which changes in physical activity outside of the exercise intervention and energy intake contribute to individual differences in body fat loss induced by exercise training programmes. To determine this, thirty-four overweight and obese sedentary women participated in a structured and supervised 8-week exercise programme consisting of 150 minutes of cycling exercise per week. Body composition, total energy expenditure and components such as exercise, activity, sedentary and sleeping energy expenditure as well as energy intake from 7-day weighed intake were determined before and during the last week of the exercise intervention. The findings indicate that overweight and obese women who during exercise intervention achieve lower than predicted fat loss are compensating by being less active outside exercise sessions. The aim of Chapter 5 was to investigate how physical, fitness and metabolic characteristics of overweight and obese women are influenced by two 8-week supervised aerobic exercise programmes with exercise sessions conducted twice per week for the duration of 75 minutes and with exercise sessions conducted 5 times per week for the duration of 30 minutes. Thirty-four women were randomised into either long and less frequent or short and more frequent cycling exercise groups. Body composition, fitness and metabolic variables were measured prior and after the intervention. The findings indicate that frequency and duration of exercise sessions does not alter the effects of an exercise programme on health related outcomes which were evident in the absence of weight loss, when the total volume of exercise undertaken is the same. Based on obtained data the following conclusions have been drawn: Overweight and obese women do not compensate in terms of appetite and energy intake for the energy expended in a single exercise session, when this is in line with recommended expenditure for individual exercise sessions aimed at body weight and body fat reduction. Compensatory responses in terms of changes in energy intake are also not evident in overweight and obese women participating in an 8-week exercise training programme. However, predicted body fat loss can be expected to match the amount of fat actually lost only in those who do not decrease physical activity outside exercise sessions. A single exercise session with energy expenditure similar to that recommended for individual exercise sessions aiming at body mass and body fat reduction, reduced triglyceride concentration by 17% in response to an ad libitum breakfast consumed 14 hours after exercise. Changes in fitness, insulin resistance, diastolic blood pressure and waist circumference in sedentary overweight and obese women induced by an 8-week exercise programme incorporating 150 minutes of exercise per week are independent of frequency and duration of exercise sessions with 2 x 75 minute exercise sessions per week and 5 x 30 minute exercise sessions per week eliciting similar changes.
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