Heart rate variability in obesity and the effect of weight loss

To investigate the effects of obesity and weight loss on cardiovascular aut onomic function, we examined 28 obese patients referred for weight-reducing gastroplasty, 24 obese patients who received dietary recommendations, and 28 lean subjects. Body weight, blood pressure, and 24-hour urinary norepine phrine excretion were measured, and time and frequency domain indexes of he art rate variability (HRV) were obtained from 24-hour Holter recordings. A measure of long-term HRV, the SD of all normal RR intervals (SDANN), was us ed as an index of sympathetic activity and the high-frequency (HF) componen t of the frequency domain, reflecting short-term HRV, as an estimate of vag al activity. All 3 study groups were investigated at baseline, and the 2 ob ese groups were reexamined at 1-year follow-up. Obese patients had higher b lood pressure, higher urinary norepinephrine excretion, and attenuated SDAN N and HF values than lean subjects (p <0.01). Obese patients treated with s urgery had a mean weight loss of 32 kg (28%), whereas the obese group treat ed with dietary recommendations remained weight stable (p <0.001). At follo w-vp the weight-loss group displayed decreases in blood pressure and norepi nephrine excretion and showed increments in SDANN and HF values. These chan ges were significantly greater than those observed in the obese control gro up (p <0.05). Our findings suggest that obese patients have increased sympa thetic activity and a withdrawal of vagal activity and that these autonomic disturbances improve after weight loss. (C) 1999 by Excerpta Medica, Inc.