Thiazide diuretics have been widely used for the management of essential hypertension, especially in patients with salt-sensitive hypertension. Most recent guidelines continue to recommend thiazide diuretics as first-line agents for all patients with hypertension in spite of the potential metabolic side effects such as hypokalemia, hypertriglyceridemia, impaired glucose tolerance and increases in serum cholesterol and uric acid. However, mineralocorticoid receptor antagonists (MRAs), such as spironolactone or eplerenone, are mainly recommended to be used in patients with resistant hypertension or heart failure because they have never been evaluated for efficacy in reducing cardiovascular events in uncomplicated patients with hypertension. In the proposed study, we planned to randomize 400 patients with essential hypertension and increased waist circumference to receive spironolactone or indapamide in combination with amlodipine for 12 months. The effects of the two diuretics on target organ damage detected by changes in left atrial volume index(LAVI) by echocadiography reflecting left ventricular diastolic dysfunction or changes in carotid-femoral pulse wave velocity(PWV) reflecting arterial stiffness and oscillatory compliance(C2) reflecting small artery elasticity will be compared. If it proves that spironolactone as first-line antihypertensive medication is more effective than indapamide in target organ protection, we would propose a large scale cardiovascular outcome trial to evaluate cardiovascular events in patients with essential hypertension and visceral obesity.