Cardiac parasympathetic activity is increased by weight loss in healthy obese women

Objective: We studied the effect of weight reduction on cardiac parasympath etic activity (PSA) in obese women. We also studied the relationship betwee n the changes of PSA, resting energy expenditure (REE), and major cardiovas cular risk factors. Research Methods and Procedures: Changes of cardiac vagal tone, an index of PSA, REE, and major cardiovascular risk factors, were measured in 52 healt hy obese women after a 6-month weight reduction. Ten of the women were reme asured at 12 and 24 months. Cardiac vagal tone was assessed by a vagal tone monitor and REE by indirect calorimeter. Results: Cardiac vagal tone increased significantly (p = 0.046), averaging a 9.5% weight loss in 6 months, The vagal tone increased further with weigh t loss during the following 6 months, and thereafter, it declined with weig ht regain. The increase of cardiac vagal tone correlated significantly with decreases of body weight, fat mass, waist circumference, serum insulin, an d heart rate. REE adjusted for fat-free mass and age did not change with we ight loss and was not related to cardiac vagal tone at any time-point. Discussion: Cardiac PSA activity increases with weight loss in obese women. This increase may not be maintained long-term if body weight is regained. The rise of cardiac PSA is correlated with decreases of body fat mass, abdo minal fat, serum insulin, and heart rate. Cardiac PSA is not related to REE .