Changes in Heart Rate Variability after Weight Reduction in the Obese

ABSTRACT

BACKGROUND: Obesity increases morbidities and mortalities due to cardiovascular diseases. In previous studies, decrease in heart rate variability was associated with cardiovascular death and reduced heart rate variability in the obese had been reported. The authors investigated immediate changes in the heart rate variability after weight reduction in obese individuals. METHODS: The subjects for this study were 39 Korean adults (35 female, 4 male), who visited obesity clinic in a university hospital from January 2002 to July 2003. At first visit, weight, height, body mass index (BMI) and waist circumference of the subjects were measured. We also measured parameters of heart rate variability Mean Heart Rate (MHR), Standard Deviation of N-N interval (SDNN), The Square Root of the Mean Squared Difference of successive NN intervals (RMSSD), Total Power (TP), Low Frequency (LF), High Frequency (HF), and LF/HF ratio. Weight reduction protocol included nutritional counseling, exercise, behavioral modification and anti-obesity medications, if needed. RESULTS: At 12 weeks of intervention, weight, BMI, waist circumference, fat mass, and lean body mass significantly decreased (3.90+/-3.11 kg, -1.50+/-1.21 kg/m2, -4.45+/-5.61 cm, -3.03+/-2.45 kg, -1.32+/-1.16 kg, P <0.01, respectively). MHR (-6.17+/-9.65 bpm, P <0.01) and LF/ HF (-0.61+/-1.56, P <0.05) showed significant reduction. Changes of weight and LF were positively correlated (r=0.338, P <0.01). Changes of waist circumference was correlated with changes of SDNN (r= 0.331, P <0.05). Changes of BMI showed positive correlation with changes in TP (r=0.327, P <0.05) and LF (r=0.345, P <0.05). CONCLUSION: Short term intervention for obese people decreased sympathetic nervous activity.