EFFECT OF ENERGY-RESTRICTED DIET ON SYMPATHETIC MUSCLE NERVE ACTIVITY IN OBESE WOMEN

Twenty obese women aged 45-65 years with borderline hypertension were allocated randomly to either a group with an energy-restricted diet or to a control group. Body weight, blood pressure, urinary sodium, and urinary excretion of norepinephrine and plasma volume were recorded. Resting muscle sympathetic nerve activity was measured in the peroneal nerve by tungsten microelectrodes and expressed as bursts per minute. These measurements were repeated after 3 days of semistarvation and after a body weight reduction of 7% while each patient's weight was in a steady state. After 3 days of semistarvation, only body weight was reduced, whereas after the long-term energy intake restriction, there were reductions of body weight (79.9 +/- 3.4 versus 74.1 +/- 3.4 kg; p < 0.001), diastolic blood pressure (93 +/- 3 versus 86 +/- 4 mm Hg; p = 0.01), and muscle sympathetic nerve activity (49 +/- 2 versus 42 +/- 3 bursts/min; p < 0.05). Other variables were unchanged. There were no changes in body weight, blood pressure, or muscle sympathetic nerve activity in the control group. We conclude that body weight decrease in obesity results in a reduction of blood pressure that is at least partially caused by a reduction of sympathetic vasoconstrictor activity.