Blood pressure and hormone changes associated with weight reduction in the obese

This study examines factors modulating blood pressure reduction in obese patients undergoing weight reduction on a low calorie protein diet. Plasma norepinephrine (NE) was correlated (r = 0.65, p less than 0.01) with blood pressure in 20 obese patients prior to weight loss. Reductions in blood pressure levels following upright posture and isometric handgrip exercise were related to reduction in NE levels after these maneuvers. While plasma epinephrine levels declined in parallel with NE levels, plasma dopamine actually increased (p less than 0.05) during the first 2 weeks of caloric restriction. Prior to weight loss the obese patients demonstrated a significant rise in prolactin levels following posture and exercise, but following caloric restriction this was not observed. Levels of plasma renin activity (PRA) and aldosterone obtained after posture and exercise maneuvers were reduced after 8 weeks of caloric restriction, and reductions in PRA were related to reductions in NE (r = 0.56, p less than 0.01). Reductions in blood pressure in association with caloric restriction in these obese patients seems to result, in part, from reduced sympathetic nervous system activity as well as secondary effects of reduced adrenergic activity on renal sodium excretion and the renin-angiotensin-aldosterone axis.