Reductions in plasma catecholamines and blood pressure during weight loss in obese subjects

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Abstract
The effect of weight reduction on levels of upright plasma norepinephrine (NE) and epinephrine (E) was studied in 20 obese patients maintained on a hypocaloric protein diet. Subjects were divided into 2 groups on either a constant 120 (n = 13) or 40 (n = 7) mmol Na intake. Initial upright NE levels were higher (P < 0.001) in obese subjects (610 .+-. 52 pg/ml) than in non-obese controls (325 .+-. 25 pg/ml). Initial NE in obese subjects correlated (r = 0.6, P < 0.01) with mean arterial pressure. Weight loss in both Na intake groups was accompanied by a progessive decline in upright NE and by 8 wk levels were decreased in all study subjects by a mean of 42% (P < 0.01) from baseline. Reductions in upright E from baseline were not as pronounced but were significant (P < 0.05) at 8 wk on both Na intakes. Mean arterial pressure and PRA [plasma renin activity] decrease significantly in obese subjects during supplemented fasting independent of Na intake. Reductions in body weight correlated (r = 58, P < 0.05) with both the fall in NE levels at 8 wk (r = 0.5, P < 0.05) and with reduction in upright PRA (r = 0.49, P < 0.05) at wk 4 to 8. Changes in upright E did not correlate with weight and blood pressure reductions. Reduction in caloric intake in obese patients is accompanied by significant reductions in upright NE and E that may contribute to the decline in resting blood pressure. The decrease in upright PRA with weight loss could result from depression in sympathetic nervous system activity.