Autonomic responsiveness in obesity with and without hypertension.

Evidence from animals models of obesity, eg the ob/ob mouse, and from studies in man are consistent with the autonomic regulation of brown tissue being one of the principal pathways involved in the normal thermogenic regulation of energy balance. Studies in man on other components of the sympathetic nervous system do not suggest generalized autonomic abnormalities in obese patients. Patients placed on a reduced carbohydrate intake show a fall in metabolic rate, a reduction in cardiovascular indices of sympathetic activity and a fall in venous noradrenaline concentrations. The hypotensive effect is accompanied by a precipitous fall in hydroxy-methoxymandelic acid excretion. These changes are not nearly so evident in those obese patients who are also hypertensive so there may be altered control of catecholamine metabolism in obese hypertensive patients.