This thesis examined the time course of the reversal of high fat diet-induced leptin and insulin resistance with endurance exercise. To this end, 96 female Sprague Dawley rats received 'ad libitum' access to a diet high in saturated fat (60% kcal) for 4 weeks with the purpose of inducing insulin and leptin resistance. Half of these rats remained sedentary, while the other half embarked on a treadmill training program during the subsequent 4 weeks. Four weeks of HF feeding impaired insulin stimulated glucose uptake and completely prevented the leptin-stimulated increase in palmitate oxidation rates. Exercise training restored insulin stimulated glucose uptake to normal levels within one week. However, the ability of leptin to stimulate FA oxidation was not restored until 2 weeks of exercise training. In conclusion, endurance exercise can restore leptin response in leptin resistant skeletal muscle. This event, however, is not a prerequisite for improving skeletal muscle insulin response.