[Cardiovascular response to the cold test in obese subjects. Effect of a hypocaloric, normal sodium diet]

Loss of weight in obese patients, both hypertensive and normotensive, causes a fall in blood pressure (BP) through a mechanism which is still not fully understood. The effects of a low-sodium low-energy diet on BP were assessed in 20 obese subjects (15 M and 5 F; age 26-65 years), 11 of whom were normotensive and 9 hypertensive. Following a period of normocaloric diet, a diet of 600 kcal was prescribed for 6 months. BP and heart rate (HR) were measured at the start and end of hypocaloric diet in resting conditions and during stimulation of the adrenergic nervous system (ANS) obtained by exposure to cold (immersion of the hand in water and ice). A reduction of resting BP (from 137/81 +/- 5/4 to 122/74 +/- 4/4 mmHg, p less than 0.05) was observed in 8 patients who lost at least 30% of excess weight (from kg 107 +/- 6 to 91 +/- 4, p less than 0.001) together with an increase in BP during exposure to cold (from 140/82 +/- 3/3 to 156/95 +/- 7/4 mmHg before and from 120/78 +/- 3/4 to 140/88 +/- 3/3 after the diet, p less than 0.05). No changes were found in the daily urinary excretion of Na during the course of diet therapy. These results demonstrate that a hypocaloric diet, independent of saline restriction, is able to reduce resting BP and pressure peaks during adrenergic stimulation.