Obesity and hypertension: epidemiology, mechanisms, treatment

There is a close epidemiological association between obesity and elevated blood pressure for all age groups, although not every obese individual becomes hypertensive. In populations without age-related increases in body weight, an elevation of blood pressure with age is not seen. Mechanisms included in the development of hypertension in obesity are hyperinsulinemia, insulin induced sodium retention and increased sympathetic tone. Overnutrition with over intake of sodium and lack of physical exercise contribute to the metabolic syndrome of obesity. Thus, weight reduction by decreased energy uptake and increased physical exercise is recommended in the treatment of hypertension in obese patients. The resulting fall in insulin levels may lead to decreased sodium absorption in the kidney. Although treatment of obesity by weight loss decreases blood pressure substantially, a minority of patients do not respond to the weight loss. Blood pressure generally decreases before normal weight is achieved. Salt intake reduction does not appear to explain why weight reduction lowers blood pressure. Reduced levels of plasma renin activity, serum aldosterone levels, catecholamine levels and serum insulin levels may be involved in the blood pressure lowering associated with weight loss. Since the risk of cardiovascular disease in the hypertensive patient is not only determined by the blood pressure, an overall treatment which aims at reduction of other risk factors such as glucose intolerance and hyperlipoproteinemia is advocated. Thus, in any obese hypertensive patient normalization of excess body weight and increased physical activity appears to be the first and most important step of any rational therapeutic strategy.