Effects of short-term hypocaloric diet on sympatho-vagal interaction assessed by spectral analysis of heart rate and blood pressure variability during stress tests in obese hypertensive patients.

We examined the effects of a short-term low-calorie diet on the activity of the autonomic nervous system during stress tests in obese patients with hypertension by analysis of heart rate and blood pressure variability. Eighteen obese inpatients with essential hypertension were given a regular-calorie diet (1,600 kcal, NaCl 7 g) for 4 days, and then a low-calorie diet (1,100 kcal, NaCl 7 g) for 11 days. During both the regular-calorie diet and low-calorie diet, power spectral analysis of heart rate and blood pressure variability at rest and during mental arithmetic test, deep breathing test, isometric handgrip test or cold pressor test was performed. Body weight and 24-h ambulatory blood pressure were significantly lower during the low-calorie diet than during the regular-calorie diet. Systolic and diastolic blood pressure significantly increased over the handgrip test and cold pressor test during both diets. The low frequency component (LF) of systolic blood pressure, a marker of sympathetic activity to the vasculature, during the deep breathing test and cold pressor test were significantly lower on the low-calorie diet than the regular-calorie diet. The blood leptin concentration was also significantly lower on the low-calorie diet than the regular-calorie diet. The decrease in body weight was positively correlated with the decrease in blood leptin concentration. The LF/high frequency component (HF) ratio of the RR interval at rest on the regular-calorie diet was negatively correlated with the decrease in blood leptin concentration. These results suggest that the autonomic nervous function assessed by analysis of heart rate and blood pressure variability during stress tests may be improved by weight loss due to a short-term low-calorie diet in obese patients with hypertension.