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Mark E Smyers, Ph.D., August 2019School of Biomedical SciencesDietary Restriction, Physical Activity, and Metabolism; Potential Role of Intermittent Fasting for Reducing Obesity (141 pp.)Dissertation Advisor: Colleen Novak, Ph.D.Abstract:Obesity and the associated metabolic dysfunction cause serious harm to human health. These studies investigated the role of physical activity in weight loss in rat models of obesity and leanness. A method was first developed to analyze weight changes, food intake, and physical activity over long term in rats by comparing macronutrient-biased diets. Then, using a model of two lines of rats selectively bred for either high intrinsic aerobic capacity or low intrinsic aerobic capacity, a 50% calorie restricted diet was used in one experiment and intermittent fasting was used in another experiment while continuously monitoring physical activity and food intake over long periods. The specific effects of the diet were dependent on the aerobic phenotype of the rats, which normally are lean (high aerobic activity) and obese (low aerobic capacity). The high aerobic capacity rats lost most of their fat mass during calorie restriction but rapidly regained it back during refeeding periods. Low aerobic capacity rats responded best to intermittent fasting and lost so much weight that they became similar in weight and adiposity to the lean, high capacity rats. A possible mechanism (heat-shock proteins) was explored to explain the difference in response between the high intrinsic aerobic and low intrinsic aerobic rats to calorie restriction or intermittent fasting by thermally treating rats in a water bath or administering geranylgeranylacetone (a known Hsp70 inducer). There are hints that Hsp70 may be involved with the different diet response but further research confirming its involvement is required. These studies support the potential of intermittent fasting for a method to lose weight and adiposity in those with low intrinsic aerobic capacity predisposed to obesity. |
