No abstract

SUMMARY 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 < 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 < 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 < 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-angiotensinaldosterone axis. (Hypertension 4: 686-691, 1982) KEY WORDS • obesity • blood pressure • catecholamines

A group of 10 borderline hypertensive obese subjects had higher (P less than 0.05) supine plasma norepinephrine (NE), epinephrine, and PRA levels as well as greater (P less than 0.05) NE responses to upright posture and isometric handgrip exercise than 12 nonobese controls. Plasma NE as well as mean arterial pressure (MAP) responses to posture and handgrip in the obese patients demonstrated a significant decrement at week 2 after the onset of a low calorie diet. Decrements in plasma NE and MAP responses to posture were correlated (r = 0.61; P less than 0.05) throughout an 8-week period of weight loss in these borderline hypertensive obese subjects. In 15 normotensive obese subjects as well as in the 10 borderline hypertensive obese subjects, weight reduction associated with a very low calorie intake was accompanied by a reduction in supine plasma NE, epinephrine, and MAP 2 weeks after the onset of dieting. PRA decreased after 8 weeks of dieting in both obese groups, and these PRA decrements were correlated with reductions in MAP and decrements in plasma NE. We conclude that enhanced sympathetic activity may play a role in the maintenance of elevated blood pressure in obese individuals. Decreases in PRA and blood pressure associated with weight loss in both normotensive and hypertensive obese individuals occurs, in part, secondary to reductions in plasma NE levels.