Effects of acute and chronic exercise on appetite regulatory hormones, craving and body weight in sedentary lean and overweight/obese females

The thesis comprises of two major parts; firstly, the responses of overweight/obese and lean females´ body weight and selected appetite-regulating hormones (fasting and postprandial) to an 8 weeks exercise-training program avoiding bias towards weight loss by internal and external motivation were investigated. A single blind design was conducted with concealed aims and objectives and exclusion of individuals with intention to lose weight. Overweight/obese (OV/OB) (n=23, BMI= 30.27±3.66 kg m-2; age= 23.39±5.70 years) and lean (L) (n=11; BMI= 22.41±2.14 kg m-2; age= 24.55±6.93 years) completed the study. Results: both OV/OB and L groups resulted in no significant changes in body weight. Of the selected appetite hormones, amylin levels were significantly altered in the OV/OB group affecting fasting and postprandial amylin with reductions (-24.2% and -14.1%, respectively); no changes were detected in L group. Multi regression analysis revealed that leptin and postprandial amylin levels were significant predictors of BMI changes after the exercise intervention explaining 45% of the variance in the OV/OB group. Conclusion: The findings suggest that under ad libitum condition, un-biased by internal and external motivation for weight loss, 8 weeks exercise training did not result in weight loss in overweight/obese and lean females. Secondly, the effects of acute exercise bouts of moderate and high intensity on food craving dimensions, implicit and explicit attitude towards food, and on selected appetite hormones in lean and overweight/obese sedentary females were investigated. In the second part two studies have been conducted, a pilot study with lean sedentary females (n=10, BMI= 21.93±2.16kg m-2, age= 23.50±2.95years) and a trial with 19 sedentary females (lean individuals (L) n=9, BMI= 20.94±2.84kg m-2, age= 21.56±2.66 years; overweight individuals (OV/OB) n=10, BMI= 29.51±4.31kg m-2, age= 23.70±5.05years). In the trial females performed one high (HI) (90% O2peak) and one moderate intensity (MI) 50% O2peak)exercise bout on cycle ergometers with matched energy expenditure in a counterbalanced design, followed by a test meal. Selected appetite hormone measures were taken at fasting, pre exercise, post exercise and 1 hour post exercise. Food craving questionnaire-state (FCQ-S for savoury and sweet foods) measures were taken at fasting, postprandial, pre exercise, post exercise, 1 hour post exercise, post-test meal and 30 minutes post-test meal. Results: An acute bout of exercise, at both moderate- and high-intensity, resulted in a significant suppression of appetite for both sweet and savoury foods in OV/OB individuals (P 0.05). With regard to hormonal response; the findings indicated that an acute bout of exercise result in a significant reduction post-exercise in amylin concentration, with the greatest response evident following the high-intensity protocol where amylin was reduced from pre- to 1h post-exercise by 46% in OV/OB group. The study also demonstrated that OV/OB individuals have a greater drive to eat in a postprandial state following the ingestion of a 300 kcal test-meal. Conclusion: OV/OB females experience a larger decline in craving after exercise than lean; otherwise, this might be overcompensated by the increased craving in the postprandial state by OV/OB. The collective findings of this thesis suggest that the utility of exercise alone as a mediator of weight loss seems unsupported at least in the limitations of gender and exercise duration used for our research design. Our investigations in both lean and overweight females suggest that exercise should be used in conjunction with dietary restriction to maximise the chance of success for weight loss programs. Studies that have formerly reported weight loss in females may be confounded by the participants desire to lose weight during the study, exhibiting increased self-control in their eating behaviour alongside the exercise intervention.