VLCD-induced weight loss improves heart rate variability in moderately obese Japanese

To evaluate the effects of weight reduction on the autonomic nervous system in obese patients, we investigated heart rate variability (HRV) based on 2 4-hr ambulatory electrocardiogram (ECG) recordings before and after weight reduction. To aim for weight reduction, 16 obese patients were treated with the very-low-calorie conventional Japanese diet (VLCD-CJ) therapy combined with behavior therapy. Percent weight reduction was 17.8% +/- 1.5% (means +/- SEM), but mean blood pressure did not change significantly after VLCD-C J therapy. The mean normal R-R interval (mNN) of the 24-hr ECG and all othe r five time-domain indices increased after weight reduction. Spectral analy sis revealed that weight reduction increased the high frequency (HF) compon ent, but decreased the ratio of low to high (LF/HF) components. Rate of cha nge in mNN or HF correlated positively with reduction rate of body mass ind ex, but not that in LF/HF, Analysis of daily fluctuations in each HRV param eter showed that significant improvement after weight loss occurred mainly during the nocturnal period, but an HF component was improved throughout th e day and night periods. These findings indicate that functional impairment of the autonomic nervous system in obese subjects, particularly in the noc turnal period, is improved by effective weight reduction after VLCD-CJ ther apy.