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

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) mmole sodium 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 sodium intake groups was accompanied by a progressive decline in upright NE and by 8 weeks levels were decreased in all study subjects by a mean of 42 per cent ( P < 0.01) from baseline. Reductions in upright E from baseline were not as pronounced but were significant ( P < 0.05) at 8 weeks on both sodium intakes. We have previously shown that mean arterial pressure and PRA decrease significantly in obese subjects during supplemented fasting independent of sodium intake. In the present study reductions in body weight correlated (r=58, P < 0.05) with both the fall in NE levels at 8 weeks (r=0.5, P < 0.05) and with reduction in upright PRA (r=0.49, P < 0.05) at weeks 4 to 8. Changes in upright E did not correlate with weight and blood pressure reductions. We conclude that 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.