Heart failure with a normal ejection fraction (HFNEF, previously termed diastolic heart failure), accounts for the majority of heart failure cases in the population > 65 years old and has been recognized as a true geriatric syndrome. Exercise intolerance is the primary chronic symptom of HFNEF and a major determinant of these patients' severely reduced quality of life; however little is known regarding its pathophysiology and treatment. Therefore, our work has focused on understanding the pathophysiology of exercise intolerance in HFNEF and developing and testing interventions that may improve this pivotal outcome in this highly prevalent disorder of older persons. The aims of the proposed study are to conduct a randomized, controlled, single-blinded, 2x2 design trial to examine the effects of weight loss via hypocaloric diet, aerobic exercise training, combined hypocaloric diet and exercise training, and attention control in patients with HFNEF and body mass index >30 in order to test the following hypotheses: 1) Both weight loss and exercise training will improve exercise intolerance and quality of life in older, obese patients with HFNEF; 2) The combination of weight loss and exercise training will produce complementary effects on body and thigh muscle composition and additive improvements in exercise intolerance in HFNEF; 3) Improvements in exercise intolerance will correlate with improvements in lean body mass, reversal of adverse thigh muscle remodeling, and increased thigh muscle capillarity. The study has the potential to significantly advance our understanding of exercise intolerance and its treatment in the large population of older persons with HFNEF.