Excess weight gain is a major cause of essential hypertension, and abnormal kidney function appears to be a cause as well as a consequence of obesity hypertension. Excess renal sodium reabsorption and a hypertensive shift of pressure natriuresis play a major role in mediating increased blood pressure associated with weight gain. Activation of the renin-angiotensin and sympathetic nervous systems and physical compression of the kidneys appear to contribute to obesity-induced increases in sodium reabsorption and hypertension.