Blood Pressure Control During Weight Reduction in Obese Hypertensive Men: Separate Effects of Sodium and Energy Restriction

The separate and combined effects of dietary energy and sodium restriction on regulation of blood pressure were investigated in 30 middle aged obese men with essential hypertension attending the outpatient department. In group 1 (n = 15) a basal period with no dietary restriction was followed by a period taking an energy reduced diet (5.1 MJ; 1230 kcal), the sodium intake being supplemented and hence unchanged (1:ErSn). In group 2 (n = 15) the basal period preceded a control period with no intervention, which was followed by taking a diet restricted in energy (5.1 MJ; 1220 kcal) and sodium (2:ErSr). During period 1:ErSn there were reductions in heart rate and urinary noradrenaline output but not in systolic or diastolic blood pressure. Body weight decreased by 4.9-11.7 kg and urinary sodium excretion did not change. In period 2:ErSr urinary sodium output was reduced by 81.4 (SEM 17.8) mmol(mEq)/24 h and there was a weight loss of 8.2 (SEM 0.7) kg. Systolic and diastolic blood pressures fell significantly, as did the heart rate and urinary noradrenaline excretion. These results show that in hypertensive obese men a moderate weight reducing diet decreases indices of sympathetic nervous system activity. Reduction of blood pressure to the normotensive range was observed only when there was a concomitant restriction of sodium intake.